Online Casino

Advantages
As a general rule: the fewer the decks, the better for the player.
Double-down after splitting pairs: advantageous to the player.
Re-splitting of Aces: a clear advantage to the player.

Disadvantages
Allowing the dealer to hit a Soft 17 (It gives the dealer a chance to improve).

No dealer hole card: This variation (common on cruise ships) is a disadvantage to the player. Because the dealer does not deal himself a second card (until after the players have played), they can lose the doubles and splits.

Blackjack Variants
Las Vegas Blackjack—played with two decks. House must hit on hands less than soft 17 (17 involving an Ace). House must stand on hands of 17 or greater.
Atlantic City Blackjack—Games are played with four decks. House must hit on 16 and stand all 17's.