madno - Very interesting reading!  Your conclusion agrees with other benchmarks I read for 3DSMax. Was surprised to see in the other benchmark memory speed did not have much of an impact, the reason given in the review was the on chip memory handling.

Have heard Win8 is better at handling multicore than Win7 so is faster.

The other thought is if the idea is to do other things on the PC whilst a render is taking place the hyper threading on the i7 would make it a better choice.

Obviously going for higher clock speeds will have the negative impact that more power is required so the system will need more cooling, generate more heat and noise, and cost more to run. The new Haswell boards require less power but will cost more.