my first and only dragonite question?

You have enough candies for both, but if I were you I'd evolve the 91 IV first, for this reason:

If you evolve the 91 and it turns out with something like steel wing/hyper beam, then you can rest assured you can power it up again to sit in gyms. You still have another chance in the 76 one for a good evolve as an attacker.

If you evolve the 76 and it turns out with the steel wing/hyper, you can't exactly use it as a defender (CP and IV good, but not the best), and you'll be placing the entirety of your bet on the 91 you have remaining.

Statistically the probabilities of ending up with a good/bad moveset are equal but evolving the higher IV one first at least leaves you with a contingency plan (and if you get a desired moveset on the first try, you may not even bother with the second try)

Obviously depends on what you're looking for and your gym meta. I was just in your situation and picked a good but not great IV but level 28 Dratini because I really wanted a great attacker and didn't care about IV perfection. Alas, got steel wing/Hurricane, but since CP was around 2750 or so that was just fine to stick him in a gym, even above a Blissey, so I have a 2nd chance with over 125 candies and some decent hatches.
Good luck however you decide.