Heyas,
Only the first 177s are 150HP. All of the 177A and Bs, which are essentially 1969 and newer have 180HP, and the 177Bs got a CS prop and a different wing. For the 177s and 177As, you can get the larger engine/prop STCed. They have quite the following. There are no structural issues that I am aware of, but the center carry through spar requires a good inspection on a pre-purchase to check for corrosion.
Their "bad rap" mostly comes from pilots who were trained to drive an airplane onto the ground rather than aviate. The 177 has a stabilator, and the earlier one's had a high performance wing coupled to a low HP engine, the combination of which gave you something that was most un-Cessna like.
They are great airplanes, and the RG version is the best looking single ever made, IMHO. Like all airplanes, they have their quirks, and you'd best do your research before making the plunge.
If you are considering a two seater, you can't go wrong with a 150. There are a lot of 152 out there, but considering the comparatively short production time and the fact that there really weren't any two seaters produced for a long time afterwards, most 152 have been beat to death.
Back in the day, most schools would get a few new 150s a year, run them a bit, and then sell them off when they got "high time" of 1,500 hours or so. By the time the 152s came on the scene, things were getting too expensive to do that, and as a result, most places hung on to their 152s. When production effectively ended in 1983 (yes, I know there are later models, that's why I said effectively) there wasn't anything to replace them with, so the same 152 just flew and flew and flew.
As a result, you can get a seriously nice, relatively low time (~3-4,000 hours) 1976 or 77 150. Most 152s, OTOH, are getting close to 10k if not more, and have been tortured nearly all their life.
PA-28-140s are a good bet, too. Remember, they are really two place airplanes with a bench in the back to put yer stuff.
Cessna vs Piper? It's the same as Ford vs. Chevy. Depends on what you like. Once you figure out what you like, join a type club, like the Cessna Pilots Association. You'll get more advice then you will ever use.
Richman