To reiterate a little bit into what others have said already. You might win 20 cents more by splitting the tens or doubling the soft 20, but how many hours will you lose due to the earlier tap OR how much more risk are you creating for minimal gains that are technically mathematically correct. Of course if risk is not important to you the mathematical play is the best one in an ideal world, but in the eyes of the house the only reason you splits tens is because you are crazy, drunk, or very good. Just remember that.