IMO, here's what it comes down to...
Both are double edged swords - with the iphone you get a rock solid device with rock solid development (both the os and the apps), but limited or no option to tweak/hack the phone. With android you get open source, so you can hack and tweak until your hearts content, but software (both apps and os) update constantly, there are several version of everything out there and there is FAR less quality control when it comes to development.
Since you like to hack/tweak, I think you'll be disappointed in the long run with the inability to play with the iphone. I have a droid x, and have a fair bit of experience with the incredible. The major difference is this - do you want a bigger screen, or a thinner/sleaker device? The software differences (motorola vs HTC) are easily made up for with a rooted device, so I wouldn't let things like sense UI sway your decision.