The number of tricks each side can make is 9.266 and 9.333(no 2 suit fit). This is based on about 2,600 hands. The sum total for both side is 18.6.The result also seems to be the same for all hcp ranges(20-20, 19-21, 18-22, 17-23, 16-24).
This is the first combination which yields results that is a little surprising to me. The side that has 10 trumps do not have much advantage over the side that has 9 trumps. So having a nine trump fit is a very good situation. It does well against you opponent whether they have 9,or 10 trumps. Systems like Bergen raises which are ideal for identifying 9 trumps in the majors are superior over other systems. My own 5 card minor systems also have a big advantage in identifying 5 card minors (and thus 9 card fits).
The saying 8 ever and 9 never is true for dropping the Q.
Cheung's 1st rule of Number of trumps is 8 never and 9 ever. Be very cautious if you know you only have 8 trumps. Think twice before bidding at the 3 level or double your opponents contract at the 2 or 3 level. Be very brave if you know you have 9 trumps. You have a big advantage over your opponent if he has 8 trumps and you are just a little underdog if they have 10 trumps.
High card points is more important here. with 21 hcp for the side with 9 trumps and 19 hcp for the side with 10 trumps, The 21 hcp with 9 trumps make 9.7 tricks and the opponent makes 9 tricks. The reason is that with 9 and 10 trumps it is the A and K you have that make the most difference. So 1 hcp change means exchanging an A for a K or a K for a Q. This in many cases can lead to the difference of 1 trick. Simulation result says the difference is .75 tricks compare with both side has 20 hcp.