See if you can try both of them out in store. Everybody is going to have a different opinion. The iphone is the "popular" choice, but popular doesn't always equal best. I've never tried the Iphone myself, since I refuse to pay for AT&T's overpriced service, but many people seem to like the music and web browsing experience on it. If you listen to music often, it might be the better choice, as many HTC phones, including the Fuze, will require a separate and slightly bulky dongle just to plug in headphones.
If you can deal with that, know that you'll have many applications and features available that you WON'T get on an iphone. Being a Windows Mobile phone, you'll be able to use Mobile office, which will allow you to type papers, edit excel spreadsheets, etc. There's also tons of programs available in every conceivable category you could imagine. Just know that unless you're willing to go the "shady" route, you'll have to pay for them.
The best thing to do is decide for yourself. They're very different phones, and chances are that if you go in store and play around with them, you'll definitely end up leaning in a certain direction.