I own both devices and the E71 is a better business device in my opinion but the iphone is certainly more fun. (though I have a very usable Sega mega drive emulator running on the E71 which provides hours of play using the physical keyboard)
E71 "does the business" but certain features such as camera do lack. The E72 does address many of these and from what I have seen the camera on that model is nothing short of fantastic (though video recording is still lacking)
E71 has stellar battery life and I have full voice navigation maps operating on mine which will last a drive from Auckland to Wellington navigating (display off some of the time)
iPhone does have a larger higher resolution display however than the E71 ans E72 which are still quite low resolution
iPhone has "better" web browsing but the E71 does handle flash surprisingly well.