The main difference between single and double deck blackjack games lies in the number of decks used, which significantly influences the game's dynamics. Single deck games use one deck of cards, offering players a better chance of achieving favorable outcomes due to the increased predictability of the cards remaining in play. This often results in more advantageous strategies for players. In contrast, double deck games utilize two decks, which can dilute the effect of card counting and change the strategies involved, often favoring the house slightly more than single deck games.