If you are strictly counting cards and you play a strong enough game to beat the 6:5 tables, why would you be wasting your time on 6:5?
Now if you're HC'ing, that's another story. Or if you're employing even stronger techniques, then the 6:5 game is the way to go, IMO. I have at least two reasons why I believe this to be so:
1) Lack of heat - the 6:5 game probably receives the least scrutiny of all the bj games.
2) Personal satisfaction. It's especially sweet to beat these greedy bastards at a game which is designed to gouge the players.
(Obviously, the first reason makes much more financial sense than the second).
I personally will go out of my way to play 6:5 blackjack, and in the last few years I've probably derived 60% of my income from that game. And I will guarantee that it's NOT from counting!