IMO, G4s look better and the click wheel is a much better control type. It might look harder to use or worse at first glance, but don't give an opinion until you've tried it or the Mini wheel. (if you did, well... I shut up
)
I would definitely encourage you to buy the G4 one, unless the cost difference is very important to you.
Oh, and the G1/G2s definitely didn't have a click wheel.
The G1s had an actual rotating, mechanical wheel in the middle and the mechanical buttons around it. The G2s replaced that real wheel with a touch scroll wheel (the mechanism under the "hood" was the same, they only changed the outsides) but the buttons were still outside the wheel.
/ 
