I am no expert but more powerfull really depends on what we are talking about. From everything I have read here xenos is monster at VS and leaves the RSX behind. Looking at sony's edge tools it seems to back that up with sony using up to 2/7 of the cell or 2 spu to cull triangles to help it catch xenos. If I am wrong I would love to be correct on that.
Have you read the following by ShootTheMonkey?
ShootTheMonkey said:For all you might say about the dynamic allocation of vertex pipes, you end up limited by a lot more external things than anything internal to the GPU. Also, no matter what, on major passes, you're going to end up spending more effort on pixels anyway, and RSX has a moderate advantage over Xenos in that area. All the same, getting a billion triangles per second to the GPU in the first place is basically impossible. It doesn't matter how much power the GPU has to work with them because it can't get to that point. In general, the challenge in getting 100-150 million tris per second moved through the pipe is hard enough whether you're on PS3 or 360, and it's not the GPU itself that's the problem.