Who would you take in a striking match. Thiago Alves or Nick Diaz?? IMO its not even close. Alves would destroy Nick on the feet. Yet we saw GSP to be the one that dropped Alves.
For sure, in a K1 style match Alves beats Diaz and GSP. On paper, Alves is superior to them both strictly striking speaking, but half of Alves killer arsenal are his kicks and once GSP put the fear of the TD in him, Alves beat himself. He was afraid to throw the more effective half of his striking arsenal; his legs. Nick doesn't really kick or at least his kicks are not as significant to his general strike game as Alves is, so Nick can remain in the brothers Diaz hunched over, TDD ready strike stance.
GSP didn't have to put up with Alves' full striking arsenal due to implemeting the fear of the TD in Alves' head, imo. With Nick, GSP would have to deal with a closer to full potential of Nick's striking arsenal, as oppose to 40-60% of Alves' when they fought.
However, all that being said, even if you concede to the idea that Nick is more effective on the feet, GSP takes him down at will and it becomes a wrestling match, something that flusters both Diaz brothers.