From the technical side, Blackberry has more inherent security features for your high-use systems, email, browsing, legacy system connections but the iPhone is "prettier" and has more 3 rd party accommodations and is much more versatile.
In other words, if you want something that is reasonably secure...get the Blackberry. If you are not conducting business with your phone, grab an iPhone. Next year, iPhone will let companies develop corp enterprise security protocols of their own using the source code back-end I believe so it will be as secure as enterprise Blackberry servers at that time...according to the info roll-out by Jobs a few weeks ago.
I will stick with my Blackberry Storm
V/r
Changeup