The same can be said for the 12 V 4 decision. Per the Illustrious 18, At TC = 0 or less, you are supposed to hit.
I looked online and saw the following strategy for this borderline decision -
"Hard 12 vs. Dealer's 4:
Above, I said to hit 12 against 2 or 2 [sic - 3?] but stand against 4, 5, or 6. The 4 is barely on the other side of the border. If you hit 12 against a 4, you'll win 39.67 percent of the time; if you stand, you'll win 40 percent of the time.
So what's the right play? If your 12 consists of 9-3, 8-4 or 7-5, you stand. Since that 9, 8 or 7 already has been dealt, it's not there to help you. But if your hand is 10-2, not only have you not taken out a card that could help, you've taken out one of the 10's that could bust you. And even if you're playing with six decks, that makes a big difference. If your 12 consists of a 10 and a 2, hit it; otherwise, stand--just as basic strategy tell you to do.
The gain you see by changing your play will be small, but it's a step in the right direction for those who want to go beyond the basics."
(Dead link: http://www.fringe.com/games/blackjack/10calls.php)