You have to look at how important surf is for you, and if you surf on low water areas (sandbanks/reefs).
As here you would probably prefer a short mast.
For wingfoil and kitefoil a 90 cm is the choice, conditions doesnt really matter, and shorter has disadvantages according to most riders (not all, a few like short masts)
As you have the option for 85 and 72 cm, you should pick 85 as the best compromise, as shorter is no good for wingfoiling.
But if you mostly would surf-foil, and very low water too, the 72 might be better.
And then live with the disadvantages for wing and kite