Of course, my pro's and con's are based on the CURRENT iPhone. By the time the X1 is out, there may or may not be a new iPhone.
There are some things in the X1 I don't think we'll ever see in an iPhone; a hardware keyboard, real GPS and decent enterprise support. Yes; the iPhone is getting Exchange, but there are still things you can do with a WinMo device that I don't see an iPhone ever doing.