not really familiar with the g22, but, I prefer gen 4 over gen 3 glocks - got both (3 gen 4s & 2 gen 3s)
I don't believe that a gen 4 g22 would be "less snappy" (and I've not encountered "snappy" with reference to .40cal) - by the way, I've got a g24 (.40cal) and like it mucho (and like .40cal too - have 2 .40cal pistols - my next pistol will be a .40cal (STI))
Personally for me it really doesn't matter. I do slightly prefer the gen4's mainly for the rtf style grip, but the price difference between the two can be a deal breaker for me. The only reason I have a gen4 G19 is because it was $450
I prefer the Gen 4. I like the grip texture better. My G22 Gen 4 shoots pretty well. Probaly my favorite 40 that I own. The two piece recoil spring is supposed to improve felt recoil over the Gen 3 but I have never shot them side by side. you also get that 3rd mag so that helps justify the cost.