Beginning card counters tend to think that the fewer decks used in a blackjack game, the better. Since there are less cards to count, it is easier to penetrate single-deck and double-deck games. But should you play them when you find them?
Before Edward Thorp shook the very foundations of casinos with his card counting classic, Beat the Dealer, only a single deck was used in blackjack. When card counting spread among gamblers, the casinos began using multiple decks. This made the work harder for the card counters, who now had a tougher time penetrating decks. Not only are there more cards to count now; these multiple decks can be and are also shuffled before the whole shoe is played! Imagine that: just when the count is getting high, the decks are shuffled!
Now obviously, single-decks seem like a better choice for card counting, right? And it should be. But casinos know what you're thinking. So now they do offer single-deck games again, but with a catch - the blackjack payout for single-deck is 6:5 instead of 3:2! This is 6-5 Blackjack and experienced players know better than to play this at all.
When you see single-deck blackjack being advertised, check the blackjack payout. If it is 6:5, don't play it.
However if it is 3:2, you should play it. In fact, if you are a card counter, you will make more money from playing a little single-deck than from playing lots of multiple-deck games.
Strategy for single-deck games is quite different from multiple-decks.
Double-decks seem to have the same superstar status of single-decks. Card counters are supposed to make a fortune off them, or so casinos think. Because of this, double-deck games often have rules designed to make them less profitable. And this is why you should think twice before playing them.
Often, double-decks have modified rules that increase the house advantage to about the same level as six-deck games. Also, the minimum wager tends to be higher. This is to cancel out any profits that card counters might otherwise make.
But if you find double-deck games with the same rules as six-deck games, the house advantage is about the same. Further, if the minimum wager is not very high, it is all right for you to play it. Basic strategy for double-deck and single-deck are very similar to each other. The chief variances lie in splitting options which are not important, anyway.
Card Counting Speed and Deck Penetration
When playing single-deck and double-decks, the tempo of the game is much faster than in six-decks. The card count fluctuates quite rapidly and the shuffle comes quickly. It is therefore challenging for the card counter who must be able to think and act faster.
As in all card counting, penetration is crucial. You want to be able to penetrate most of the deck or shoe. But since there are fewer cards in double-deck and single-deck, you can do with a relatively low penetration which would be unacceptable in, say, a six-deck game. A 75% would only be good for six-decks, but great in double-decks. The higher the penetration, the greater your advantage over the casino.