^^ Incredible S - Not exactly better primary camera. Higher MP doesnt equal to better picture, from samples i would say Desire S has far better day light picture quality.
Yes, bigger screen, cant argue with that.
But this, along with higher MP camera makes the back side downright ugly when compared to Desire S.
Both are latest phones, and Desire S is actually having 2.3 whereas Incredible S doesnt. Desire S launched after Incredible S, so, it makes Desire S the newer phone. Both have identical hardware inside, so, if HTC takes out an icecream sandwich(probably will) for any of them, it would be for both, and not just one.
Also, Desire S battery life is better than Incredible S, and better build quality too.