I use the nike+ and garmin connect. Nike+ is good for mapping and recording miles. It's great for challenging friends and smack talk. The garmin obviously is great for recording heart rate info, cadence, instantaneous pace, etc. The garmin is also superior for elevation tracking. The other day my garmin was showing just over 300' elevation gain and loss over 8 miles, which is accurate. Nike showed 2800', which is obviously in error as I wasn't rock climbing. Together, they are pretty good.
If I had to pick one or the other, I'd go garmin. But as I listen to music on my phone as I run anyways, it's easy to run the nike+ as well. It can drain the battery though, depending on the device. Last year in Vegas my 4s died at just over 22 miles. This year in Denver, I ran with music and nike+ and finished with 55% battery life left on my 5s, not bad.