strictly based on hardware and platforms (not service providers), there are several considerations that need to be examined.
the need for service of the device
whether or not upgrading memory is important or not
screen size, may be a factor
using a touch screen vs "thumbing" a keyboard (as far as I am concerned if it doesn't have a "full" keyboard, it isn't in the comparison)
total costs involved in service plans will need to be compared
the "kewl-factor" or "geek-factor" pay be part of the consideration, and is individual perceptions.
"Enterprise security" - Itunes is not a corporate friendly application and in my case is an HR offense if installed. vs. the desktop manager which has corporate enterprise versions available. This is also part of the email security. whether coming from "the Internet" or from a corporate server/post office" (non-issues for normal home users)
In my case, the BB is the only option. though I have been seriously trying to justify the purchase of an ipod touch. the main reason I haven't so far is that the max 32g is seriously a limitation to me, with no other memory upgrade options.
conclusion: assuming budgeting isn't an issue - the iphone is sleeker, and prettier, but I can't hardly think about texting/emailing/document work and doing productive work on an iphone - but you may not want to use it that way.
