There is no diffrence.
It's like the same PC in a different tower with a different monitor and a different Wlan card.
Edit:
3G has better audio chip as well (first gen did not have the same as the ipod), I forgot.
That's probably the most important difference imo, but practically it's not that much at all.
@Better built:
It's got a better metallic finish, they had to cut the price somehow, so they switched over to a different screen OEM, and made it all plastic.
If you know what the word hairline cracks mean and have owned an affected apple product, well you know what that means.
I have them on my ipods, usb-connector; Makes me giggle about how pissed I would be to have my whole phone full of nasty black cracks all over the case.
@3g:
It's cheaper now. Not the iPhone isn't worth it as a phone without a data plan (if you are not a douchebag showoff*) and they are what makes the iPhone plans so expensive.
*yea, that might kinda cover what you said now, MageMoa, but no offense it's my opinion

