ios on 3gs vs 4

[cavids]

I am upgrading to a 4s, and my son has a 3gs, so now i have to decide if I want to leave him with his 3gs, or give him my old 4. The leftover phone will go on Ebay, and the 4 sells for at least 150 mor than a 3gs on ebay.
The issue is how much slower will a 3gs be on ios5 over a 4 on ios5?

[mmaboi21]

The 4 is super fast on ios 5 so I'd imagine the 3GS shouldn't be too bad.