Blackjack Strategy When Playing a Soft 13 and 14
Double Down: When the dealer upcard is 5 or 6.
Hit: When the dealer has anything else showing.
Why to double down on soft 13 and soft 14
The reason you double down in this case is the fact that the dealer has a 5 or 6 showing, which are the two worst cards the dealer can have. Blackjack basic strategy says that because there are so many tens in the deck, it is more likely that the dealer will hit and get a 15 or 16. The dealer must stand on 17 but must hit with anything lower, so there is a very good chance the dealer would bust. This is the reason you should double down when you have a soft 13 or soft 14. It is also safe for you to get a ten in this case because the soft hand means you have an ace and if you go over 21, you still have more chances and strategy to use.
Why to hit on soft 13 and soft 14
If the dealer doesn't have the 5 or 6 card showing, then the best strategy is to take a hit. The soft hand ensures that you will not bust so it can't hurt. If you get a ten in this case, then your soft hand just becomes a hard hand. It is likely that the dealer will outscore you if there is no 5 or 6 upcard according to basic strategy in the long run so this is the best move to make.