[CyberMonkey]

It comes down to what you feel you will enjoy more.
Pocket PCs have been around for a LONG time, so there is ALOT of stuff out there on the net for them.
Given the pocket pc intergrated with phone functions is getting more popular, but way back in the day (2000-2001 time frame) alot of carrier had made add-ons for pocket pcs to turn them into phones.
Regardles the amount of stuff out there for pocket pcs are many.

Me personally I will stick with Windows Mobile devices, I have had a form of pocket pc since 2000, so I know how it works and many tips and tricks for them, very well. It's what I know.

To me the iPhone is just more of a "oh eye candy" type of thing, where as pocket PCs can be used for anything, I want to say pretty much anything an iPhone can do a pocket PC can do and most likely have been able to do it for while now.