the iphone will require jailbreaking to use "free" tethering, which can be a pain in the as*. Other than that it is a much simpler phone in general, but again at the cost of some customization, choice, and being forced to use itunes. Also apple's updates typically will break your jailbreak! The dev community and apple are almost constantly battling for control of this side of the iPhone. So you could lose your jailbreak, PDANET, and whatever else unauthorized app you pulled from cydia the next time you decide to sync with itunes so you can bump some snoop dogg on the way to french lit. Be careful!
With the RAZR you will have to "sideload" PDANET from junefabrics.net. Navigate to their site, DL the app, and DL to your device and you're done!
Like I said before, if the tethering is that important to you, then I would suggest the bionice or razr - also moto phones are going to have vastly superior signal retention, reception, and call quality. If simplicity, ease of use, intuitiveness are more important to you and you dont care about the limited "steve jobs approved" selection of apps in their app store then I would suggest iPhone. Lol this reminds me of the old PC vs MAC debate in the 90's...
Don't hesitate to post any more questions, we'll help you decide!:blink: