I have a 32GB 3GS, but I'd go back to the Pre if:

32GB Pre, or a Pre w/expandable storage

3D native gaming apps

More Apps.

I've been lamenting the shortcomings of the aesthetics of iPhone OS lately. I miss the smooth fonts and the robust web browser. I don't even use Safari Mobile very much, I use my Feeds app to get all my news and such. However, I'd use the heck out of the web browser on my Pre. I felt it was more comfortable and easy to navigate.

Gesture area is also something I really miss these days. I don't know how quite to explain it, but the Pre was so organic and fluid to navigate compared to the iPhone. I have all these apps and everything's a cluttered mess. The fonts don't look near as smooth and everything else seems boxy, where the Pre on the device and the interface it was curvy and smooth.

However, the iPhone royally spanks the Pre in the music and video playback app responsiveness. Not to mention, the camera rocks bigtime over the Pre. I'm not talking video either, seriously the auto-adjusting white balance is really good, as well as the touch interface for the autofocus/white balance adjustment. I can point the camera toward a window from inside the house and pick white balance/exposure for objects inside or outside the house.

Oh well. I can't have the perfect phone, and I'm sure that if Palm were to put this stuff into a future phone I'd be at odds with either platform for intrinsic differences

I am missing the Pre a little though. Not so much when I load up Need For Speed or Monkey Island though