This has been VERY helpful, as I'm in the same situation as Kenas. I've been going back and forth between these two units and a few others. I have been able to use my HTC Evo successfully for caching so far, (it even has a Wherigo app), but I prefer caches with higher terrain difficulty, and would like more accuracy/ reassurance. I think the screen readability in bright sunlight might be the biggest pro between these for me. One issue I've come across recently though, is that it seems like a lot of stores are dropping the 510 model...which worries me. Maybe its just a niche product since it lacks barometric altimeter and true compass? Hmmmmmm