The main difference between single-deck and multi-deck Blackjack is the number of decks used. Single-deck Blackjack, with just one deck of 52 cards, generally offers better odds for players, particularly for card counters, because it's easier to track the remaining cards. Multi-deck games, which use 4 to 8 decks, make card counting more difficult and slightly increase the house edge. While multi-deck games often feature rules that make them less favorable for players, such as lower payouts for blackjack or different dealer behavior, the larger number of cards means less frequent shuffling. Overall, single-deck Blackjack is more advantageous for players who use strategy or card counting, while multi-deck games are more challenging and typically have a higher house edge.