The Galaxy S II’s processor/GPU combo is the fastest in the mobile industry according to Anandtech with the major difference being the A5 with the SGX-543.
They said that it was the best GPU in smartphones. The processor shouldn't be radically different from any other dual A9 at the same clock speed and I'm guessing that the one in the iPhone 4S is a slower clockspeed. As for the GPU, that again will depend on what speed it is run at. There was speculation that the iPhone 4S would lose one GPU core compared with the iPad 2. It appears to have both from what information is available, but speed hasn't been specified. They may have lowered it for heat or battery reasons.
Even if you allow Apple all the benefits of the doubt here, I'm not sure it mounts up to easily arguing that it's vastly superior, "has a slower CPU, less RAM (guessing, sort-of) and a better GPU" maybe.
http://www.anandtech.com/show/4760/arms-mali400-mp4-is-the-f...
In terms of performance, the Mali-400 MP is only slightly behind the PowerVR SGX543MP2. The only major performance difference is the A5.