When playing blackjack there is only one card total that can spell success for you, but in the same time it can spell disaster. That card total is 17. You never know if you are going to win or to lose on such a card total.
Before sitting at a blackjack table, take the time to read the rules that the blackjack table follows. These are the casino's rules and it will be worth your time to familiarize yourself with them. Some casinos for example state that the dealer must stand on all 17's. This means that the dealer will not draw anymore cards if he has a soft or hard 17. This particular rule offers an advantage for the player and lowers the house edge.
The dealer will always play according to casino rules. He may not make decisions or play according to his instinct. That is why familiarizing yourself with the rules, rules such as "the dealer will stand on all 17's", may offer a great advantage for you.
When you have a soft total of 17 you will lose your advantage. Making the decision to hit in this case will only increase the house edge. The house advantage can even double now. That is why having a card total of 17 can make or break your hand. A table where the dealer will hit on soft 17's is not that favorable for the player since it has a greater house advantage. Most casinos offer both styles of blackjack (stand on all 17's and hit on soft 17's) so it may be better to find a table where the dealer has to stand on all 17's.
When the dealer is allowed to hit on soft 17's he has a clear advantage. Say for example that you have a card total of 18. That is a pretty good card total and will have a high chance of winning if the dealer must stand on all 17's. But if the dealer has a soft total of 17 (an Ace and a 6) and he is allowed to draw, he will do just that. He may easily draw a 2 and beat your 18. Even if he draws a card like an 8 he is still far from busting. In a hard total he would have busted, but since we can count the Ace in his hand as a 1, his card total amounts to only 15. He is far from busting and still has a high chance of beating your hand.
In conclusion, a blackjack table where the dealer must stand on all 17's is more favorable for the player. It is the player that gets to make all the choices, not the house. But if the house allows the dealer to hit on a soft 17, then the player will lose his advantage.