Exeggutor power up

For offense or defense?

I would power number 1 for offense for sure.

In regards to defensive powering up I would power nothing until we see the new system. Not because of the quality of the mon or movesets but because for common mons it could be a good move to just evolve higher level mons.

I'd wait to see how the new gym meta shakes out.

Both are great for defense - I actually both those mons that I used in gyms and they are both over 2700CP. Great defenders IMO.

The first one with Solar Beam is great for attacking too. Used him a bunch when he wasn't in gyms for wrecking Snorlax and Blisseys and pretty much anything else.

Wait to see what happens with the gym meta but both should be good.