Crippling Strike - question on effectiveness

[Lord_X]

I know its probably talked to death already in this Forum, but I just got to the Crippling Strike lvl. I read that this works good on all enemies who you can sneak attack but doesn't work on Orange or Red. So which one of these feats would you take first? Crippling Strike or something else?

It looks like lots are saying Slippery Mind is better to take first?

Thanks all