I'd go to a local, outdoor, range with a fitting center.  See which one is most consistent with flight and distance.  It is very important this is done outside.  If an outside fitter isn't available, go to a local golf shop and ask if you can take an 8.5* and a 9.5* with you to your club and hit them on the driving range, maybe even play a few holes with them.

hope this helps,

- Dan The Man

There is a correct answer for me, and there is a correct answer for you, the 2 answers may not be the same.

Lets see if I got this right

If  you add loft to the 8.5 you get 9.25 and the face closes promoting a draw

If you deloft the 9.5 you get 8.75 and open the face promoting a fade........also known as "preferred by better players"

Which loft will be better for you????? I believe that will depend on launch angle, swing speed, backspin rate.

Its my guess you won't see a difference between 9.25 and 8.75 degrees of loft.

BTW when you see "preferred by better players" don't pay any attention to it.

I would say leave it at 10.5 because with more loft you will get less side spin and be able to hit the ball straighter.  If you already hit it very straight, then maybe you should put it at 8.5 because you may get more distance depending on your launch angles and spin rates.