My experience has been opposite. I got my first ever iPhone today from Best Buy. Played with configurations and whatnot. Browsed the web. And made a very long call (about 50 min). My iPhone stayed cool all the time.
Before, I had the LG Optimus G for a couple of weeks. Great phone, but a bit too large (wide) for my tastes.
Anyway, the biggest problems was that the LG would turn quite warm if you did anything that uses the CPU. E.g. it would get noticeably warm after only a minute or two of browsing the web. Besides, it would drain 20-30% of its huge battery in just an hour if you actually using the phone (other than calling). But the standby on it was absolutely greatest (2% overnight).