only advantages for the 8520 is the trackpad and that there are more recent leaked versions of os 5, but that should soon become a wash when the tour catches up.
the tour2 will have the trackpad and when that comes out, which should be soon, the 8520 will be inferior everywhere.
From leaked pictures, we can only assume it'll come to Sprint. AND, brother save some money and wait for the Tour2 if the reason u want to switch to the Curve is because of the trackpad...the curve is really entry level Blackberry, and like ^ said, you'd be taking "two step backwards"... By the way, why did u want the curve...can't just be the trackpad or the looks (which aren't even appealing really)?
TOUR all the way!
wifi is a bit of a drain on battery life anyway and if your plan includes web browsing there really isnt much need for it.
as for the trackpad, tho it is easier on the thumb its a minor detail that the tour2 will have.
recently upgraded to a tour and im a happy camper.