A question about GMPs performance on the Intel Core i3 & i5 processors

[Will Galway]

I'm considering getting a new computer using, most likely, either an 
Intel i3-530 processor (my preference) or an Intel i5-570 processor.  In 
terms of the performance of GMP, is there any particular reason I should 
prefer the latter processor?  (The i5-570 has 8MB of level-3 cache, vs 
the i3-530's 4MB, but I rarely use GMP for "large" operands, rather I 
tend to work mostly with 128..256-bit operands.)

Thanks for any advice that readers might have.

-- Regards, Will Galway