The Definitive place to get impartial hands on reviews of almost every GPS watch / phone / app that there is can be found here:
http://www.dcrainmaker.com/
The guy is a triathlete and gadget freak.
I use a garmin 610 and mapmyrun. The garmin also gives me cadence from a foot pod and heart rate, so I use mapmyrun for live tracking, then import the garmin run afterwards. Its also easier to turn the garmin on and off.. button on wrist, where my iphone is on my sleeve holder thingy
