I am designing a Blackjack AI such that it would try to play optimally each hand against the dealer.
When I'm having a hard score the algorithm is easy: as long as my risk of busting is lower than the dealer's risk of busting (based on its visible card) I will hit, otherwise stand.
My problem is when I have a soft score. If both scores are under 21, I will have two probabilities of busting based on each version. I do not know however which score should I keep track of.
For example, if I have a soft 21, even though I have a 0% risk of busting the lower score on my next hit, it is better to stand since 21 is a very good score.
On the other hand, if I have a soft 15, it might be better to hit against a dealer's 2, even though the risk of the higher score going over 21 is larger than the risk of the dealer going bust with a 2 showing.
Could you please tell me if there is another parameter that should be considered regarding the soft scores (preferably easy to calculate)? If so, how should I use it on top of the bust probabilities?
N.B. The only two actions I am able to do are hitting and standing. I am not using any other actions such as doubling down, splitting or surrendering.