Which Dragonite would you power up from this group?
Dragonite 96% IV, Steel Wing / Hyperbeam, 2289 CP, lvl 24
Dragonite 84% IV, Steel Wing / Dragon Pulse, 2165 CP, lvl 23.5
Dragonite 60% IV, Dragon Breath / Hyperbeam, 2624 CP, lvl 27
I was planning on the 96% IV just for the overall CP to place at the top of gyms, but Dragons are crap defenders. I just caught the 60% IV dragon this weekend so now considering pumping him up as an attacker.
I already have a 3007 CP attacker that I use pretty often and I added a screen shot of all my dragons for reference.

Answers
Dragonite with any combination of attack is way behind Lapras or Snorlax in defense. Dragonites never were good defenders, that double weakness to ice just too much to be top tier. That big CP might look strong, but truth is one 2k CP Lapras cut through three 3k Dragonites without big problems. And while someone might counter that not everyone have Lapras, Shellder works in similar fashion, you might need 2 of them though for 3 dragonites, but dragonites in gym is easy job, just like gyarados. Big punching bag, no trouble.
It's arguably the 3rd best defender in the game(maybe 4th for Vape fans), hardly a punching bag. Definitely not the same tier as gyarados as you say.
Btw I'm lvl 33 with no double ice cloyster. No 2k lapras. So....yea maybe not everyone has ice Pokemon as someone else also mentioned.
Maybe I didn't the memo that only snorlax and lapras should be defenders.
If you want another attacker, you could even consider the 58% DB/DP at 2539 CP. It's only a couple of levels behind the 60% one, and it has 15 attack IVs. The 58% also has a higher max CP than the 60%.
Out of the 58% and the 60%, the biggest difference is the charge move, which comes down to personal preference.
But if you need a defender, the 96% is a good choice.
Edit: I agree with the other commenter, the 58% and 60% are already good enough to attack with, so you could save candies for a better IV or DB/DC attacker.
i personally wished dragonite was a good defender, so they could make him useful with steel wing. unfortunately hes an inferior defender to snorlax and lapras. hes on the exeggutor level in terms of defense. so to me, any dragonite with steel wing is useless asnd shouldnt be powered up.
however, as an attacker i still think hes the best, despite what this site says about snorlax being the alpha. his dragon breathe is deadly and attacks so quickly. any of the three charge moves will do. so basically your highest iv one with dragon breathe.