So, I've spent the last couple days playing with the free trial versions of Garmin Pilot and Avilution Aviation Maps and thought I would share a few thoughts/comparisons for those that are also trying to find the best nav app for Android. I tend to get wordy, but I'll try to keep this post from becoming a novel while still covering what is relevant. I know there are some free apps out there that are somewhat decent, however, I value the more mature and easier to use interfaces of the better rated pay-apps. So, if you prefer free (and who doesn't?), but don't mind having a little bit inferior of an app, hey, more power to ya, go for it. For me, I'm willing to pay for the better usability over the free apps.
For comparisons sake, with each app, I did some regular VFR navigation and flew a GPS and ILS approach, and then explored the flight planning and wx/briefing tools while on the ground. Also, I have only about 2 days of use with each of these apps, so it is entirely possible, maybe even likely, that a capability that I think doesn't exist or deficient may actually be possible and I just haven't discovered it yet, though I have read fairly well through the manuals of both apps and hope that this isn't too much the case.
If you are a tl;dr type: Go with Avilution Aviation Maps. If you want to know how I came to that conclusion, read on.
I'll have a lot to say with regards to the UI, as in my opinion, the quality of an app for this purpose is greatly affected by how easily you can access, display, and use the features that the app can offer. They all offer moving maps, with overlays of wx, traffic, etc. They all offer geo-referenced approach plates and airport diagrams. So, how easy are they to use?
User Interface:
The overall appearance of the UI and responsiveness in use of Garmin Pilot (GP) is a little bit cleaner and faster than Avilution AvMaps (AAM). GP simply looks more professionally designed (but not by much), as it probably is, considering the overall aviation navigation experience of the corporate parent involved in its design. 'Buttons' are easy to read on both apps, however, on my Nexus 7 (2013), GP seems to be slightly more responsive to touch inputs when touching an airport or waypoint on the map. AAM sometimes lags little bit in comparison, sometimes even requiring touching the map again to get the info box to open. GP also seems to handle the high-res screen of the Nexus 7 better than AAM as well, though AAM is still quite good overall. For exmaple, when at tight zoom levels on GP, the sharpness is held just little better than the rendering achieved through AAM. I also prefer GP's method of displaying waypoint information when you touch it on the map, with its radial button array allowing quick access to the variety of things you might be looking for. AAM works pretty well with what it shows when touching a point on the map, but I feel that it is a little bit behind in it's UI design in that the box that pops up has fewer 'buttons' but still manages to cram more words for you to read while assessing what it is that you want to choose from. It's not hard to use what pops up in AAM, I just personally prefer the appearance and layout in GP. Another benefit of GP over AAM is that GP also lets you tap on more waypoints/navaids to open an information box about said item. See a VOR you want to direct-to? Just touch and hit Direct-To on the box that pops up. AAM will sort've do this. If there is a VOR collocated with an airport, and you want just the VOR, you'll never get it. Only the airport info box will pop up, which sure, you could eventually get to the navaid info, but it involved more steps than on GP in this method.
Despite all that praise for GP, there are a similar amount of things that I dislike about it compared to AAM, and unfortunately for GP, are big enough issues that lead me to prefer AAM. For example, GP does not have an HSI overlay on your map position! In order to see an HSI in GP, you have to open the split-screen function and show an HSI in the other half of the screen, along with some other silly digital 'steam gauges' that also don't readily display on the map. AAM shows an HSI overlay on your position on the map; that is an instant plus for me, and quite honestly, a pretty big deal. That seems to be quite a big oversight on Garmin's part to not include such an item. Next in AAM's favor, you get your GS, Heading, ALT and VS placed directly above your aircraft icon on the map, but not in a manner that is obtrusive or unsightly. I could do without the ALT and VS simply because it isn't a reliable piece of information from a tablet GPS system. In contrast, GP displays all of your flight data (GS, Heading, ETE, ETD, Next WYPNT, etc etc) in a row on the top of the screen, but there are so many items listed in the row that you have to swipe on the row left and ride to see everything! Granted, you can open up the split-screen function and again show these things there, but they don't go away on the map screen when in this mode, so it just eats up map space and is a pain to use. I dislike this all of this.
Both apps allow you to receive a briefing and file through your DUAT(S) account and have all of the text based WX information you want for your route of flight, however so far as I can tell, only AAM also downloads WX maps and charts (radar pictures, freeze levels, etc). I like this. They're about equal in terms of how quickly and unobtrusively you can access this information, which is to say that I can have text WX data/radar pictures on one side of the split-screen while still seeing my map position on the other side with either app. Both allow overlays on the map of all the radar/TFRs/satellite, etc, and they're both easy to make that happen.
I prefer slightly GPs method of accessing approach plates and procedures over AAMs. In GP, you can create 'binders' loaded with just the plates/procedures you want and then name the binder whatever you want to call it, or you can create a binder that contains all procedures and documents for specific airports (say, your departure and arrival airports). You can view and open your binders in the split screen while still monitoring the moving map. I like this better than AAMs process, where you can still see the list of procedures for an airport in the split screen, however AAM does not have a 'binder' capability (that I can tell), and instead it will just show a list from a drop-down button your 8 most recently accessed procedures. Not bad, but I don't prefer it.
A big gripe that I have with both apps is that the 'nearest' function only allows you to search for nearest airports. Want to see what the nearest navaids, intersections, or waypoints to you are because you just received an amended clearance in flight and you just need a specific navaid for example? You can't do that. This I just don't understand. My 12 year old garmin 430 can do this. Why can't these new-fangled apps do it? I'm going to be looking at nearest navaids, intersections, waypoints, etc more often than I am nearest airports, especially considering that I have a moving map that can show me where I am in relation to the airports visually!
Creating and altering a flight plan is pretty simple in both apps, so I won't go into the technical aspect of it much. You can insert departures/arrivals into your flight plan, use victor airways and they will include all of the appropriate waypoints/navaids along your route. This is nice. However I'll still have to give the nod to AAM. Building your flight plan is a little bit more intuitive and much much easier to see your nav log than on GP. Which brings me to another problem I have with GP: the nav log for your flight plan is so far as I can tell not visible while in split-screen mode or even while the map is being displayed (AAM allows this), and in order to see your nav log in GP you have to dive a few menus into the Flight Planning pages to see it. I want to be able to quickly see my nav log information and still see the map, and AAM has this covered pretty well. In fact, I was nearly convinced that GP didn't even provide a nav log, which would have been a huge faux pas, as it was so hard for me to find, as I was expecting it to be short and simple from the map screen to access it.
Battery Life: Slight Edge to AAM (maybe).
Using my 2013 Google Nexus 7 set to full brightness, I was getting a battery discharge rate of about 20% per hour of use with GP. That is in my opinion, quite acceptable. I would then expect to get at least a solid 4 hours of use on one battery charge before getting concerned about it.
With AAM, so far I seem to be getting about an 18% battery discharge rate per hour with my screen at full brightness. However, it is entirely possible that the variation between the two is not directly related to the performance of the apps and more about the specific conditions of the tablet in that moment. Regardless, about 20% discharge per hour seems reasonable on my device with either app, and I consider that to be pretty good. This isn't an issue if you can connect to a USB power source in the cockpit or have 30minutes to an hour to recharge between flights at the FBO/hangar, etc.
Conclusion:
Ultimately for me and my needs (wants), I value the HSI overlay on the map, the less cluttered display of flight data, and the slightly better flight planning UI of AAM than I do the slicker (slightly) graphics of GP and it's procedure 'binders'. On top of it all, Avilution's premium subscription to include geo-referenced approach plates and airport diagrams is about $40 cheaper than the comparable subscription from Garmin. That so far has lead me to favor AAM over GP, and when the free trials are up, I expect myself to go with a premium AAM subscription.
Hope this helps!