Difference between Swiftech blocks.
 

I've been after this block for a while as i know it's a favourite with a few people around here. And it's a great price.

But i've just noticed this Swiftech block that available to me for about £10-£15.

Would the drop in performance be that noticable that it would be worth paying the extra for the more expensive? Or would they both be the similar performance-wise?

I think it will be pretty similar performance wise.