1.9GHZ VS 1.2GHZ

[xsacha]

It depends on how much the game uses both the CPU and the GPU. Each game is different but it is definitely possible that a 1.2GHz device outperforms the 1.9GHz one.

Anyway, now that you've named the devices, I can break it down for you.
Component: SGS2 v SEXperia LWW
CPU: 1.2GHz Cortex-A9 vs 1.9GHz Cortex-A8
GPU: Mali 400MP4 vs Adreno 205

First off, their CPUs can't be compared equally like this because they use different architectures. So, I will level the playing field for you (I'm being generous on the A8 too):

Component: SGS2 v SEXperia LWW
CPU: 1.2GHz Cortex-A9 vs 1.3GHz Cortex-A9
GPU: 2-3.0x FPS vs 1.0x FPS
http://gfxbench.com/compare.jsp?D1=SonyE...+S2&cols=2

The SGS2 is much much better. You will get roughly 3x the FPS in most games due to that GPU and you can play much more powerful games.
The CPU is still better, when overclocked, on the SEXperia but the difference is not that great. They are both enough to get 60 VPS in most games.