I was pondering a similar question myself some time ago. Perfect attacking moveset (breath and claw) with really bad IV's VS. good IV's and 2nd best attacking moveset (breath and pulse). I did some calculations/estimations and if I got it right, the better moveset with horrible IV's would have resulted better attacker. Thing is, Dragonite's base attack is so high (250) that the difference from the extra from IV's (max 15) that is added to base attack does not count for much.
For defense things work little differently, so I can't be sure, but I would lvl up the 80% IV's with perfect defensive moves.