What level are you? I'm pretty OCD so I would go with the 100% as your current Exeggutor is already rather good as it is, doesn't really require powering up.
I was in a similar situation myself, I had 2250 CP Exeggutor at something like 73% IV with Zen Headbutt/Solar Beam, but I powered up a 1200 CP Exeggutor with the same moveset as it had 93% IV.
Also, my strategy has been to power up 2 of each competitive Pokémon, one for defense and one for offense.