Um . . . they're pretty much the same in this case, man.
Both involve a change in form which gives a buff in certain areas (e.g. movement speed, attack speed) at the cost of others (e.g. range, safety).
The difference is that Valor is on a 140/110/80 second cd and ends in the most pathetic "execute" in the game (its damage caps at 400+100%bonus AD, and that's when the target is at 0% health), whereas cougar form is on a 3 second cooldown, and has no half-assed execute.
I'm not necessarily with the OP in saying it should have no mana cost. But I think it should be reduced. And it'd be nice if Quinn and Valor had separate cooldowns, so you could perform your combo and then ult for a finisher without waiting 12 seconds.
Edit: Um, what? Did you really just downvote me, and then edit your post to answer my argument? I do not remember that last line being there. I'll believe you if you say it was a coincidence, but you should make it obvious you're editing the post if you do it in response to a comment.