Exeggutor power up question

Not a bad moveset - he'll be versatile as a decent attacker and defender. I'd be tempted.

I'd go for it, but its your call

If you are wanting to put it in gyms, Confusion is a lot stronger than Zen Headbutt. If you like to dodge as many attacks as possible, one Confusion fits better than two Zen Headbutts in between most attacks, so it is also better on offense.

Its a monster to attack, very useful. Power it up.

A Seaking around 1000–1250 CP with Peck and Megahorn is enough to beat this Pokémon.

IMO, I would power it up. Good move set, good IV, strong in the current meta. It can be used effectively as an attacker or defender. Sure, there are plenty of answers to it. But the game overall is a game of rock, paper, scissors. I enjoy attacking/defending gyms, am just about to hit level 26 and am a casual player to give my comment some context. I have 5 mons ranging from 1811 - 2059. I find I just enjoy the game a little more that way.