Testing how speedy the iPhone 3G S "S for speed" really is has become de rigueur. iLounge has put together two videos comparing the facility of the 3G S to the 3G, last year's iteration of the iPhone, and to the second generation iPod touch.
The operator tests four applications: Edge, Peggle, Real Racing, and Star Defense. They are all graphically heavy games with initial load times, and likely where the difference will be most exaggerated. As is to be expected from a phone named for its swiftness, the 3G S outstrips both the 3G and the iPod touch by a fair margin, though the iPod touch counters the 3G S a bit more easily than the 3G does.
The videos don't offer any quantitative analysis, nor are they exact by any stretch of the imagination (you'll just have to trust the device operator to touch the application icons simultaneously), but it's comforting to know you that if dropped at least two bills, it was for a reason. Because the videos don't offer any guidance as to which device is where, I'll clue you in: in both videos, the 3G S is on the right.