Specialized. I tried Adidas and the insoles seem like they were taken from a pair of checkered Vans. I tried Sidi's 5.5 model and they didn't fit right and cost a fortune. I got the Specialized S-Works and got way more stiffness than the Sidi for $100 less, and a better enclosure system.
However, you may not be able to afford the S-Works, but the lower-end (but still high-end without the Sidi pricetag) shoes were still awesome.
I've got a pair of the Specialized BG Pro MTB shoes that are awesome.