I bring both my iphone and a garmin gps, and keep the phone off to save battery life, so I've never compared how the two match up. It'd be interesting to do that.
I don't have many apps on my phone though, and seldom use it. I do like having it when I'm backpacking though. There's not too many place you can't get a signal here anymore so it's pretty sweet to have along.
"You want to go where?"