Optimiser says need more xy and less ab, but doesn't choose that

I’ll find a way to do that thing where I can post a string that’ll show you the whole story when I can figure it out, but just for now is there any reason why the optimiser would say “Better gear than yours often has less haste and versatility, and more crit and mastery.”

Then pick between boots where the only differences are the secondary stats showing

28 Critical Strike, 53 Versatility.
32 Critical strike, 50 mastery.

and pick the top one with less critical strike and just three more versatility vs the mastery it says I want?


Thank you for the reply.