Best Snorlax?

I'd power it up until 3000-3100 CP if you live in a high turnover area. Body Slam hurts the attacker. However if you live in a low turn over area it might be a different case, because the CP decay

Most people on this site will tell you not to power up one at all because you shouldn't use them for attacking and gym defense is not really part of the meta. I would stop short of that, because everyone plays the game differently but would caution against powering up any of these options (or at least wouldn't max them, maybe go to level 35 at most since there isn't enough of a difference between 35 and 40 to be worth the dust and candies). If I were to power one up, it would be one of the body slam ones, as that move is tricky on defense. The 100% is way to low and would require so much dust and candy that there is no way to justify it regardless of your feelings of gym defense. I guess it really just boils down to a few questions. In your local meta is gym defense a thing? (Like for my area, a stacked gym with Chancy/Blissey/Lax/etc will actually last for a good chunk of time but anything really weak, will not). Do you have some personal attachment to these mons that would make you want to power them up? If you answer yes to either then sure, go for it. If not, I wouldn't.

100% snorlax is something I would max just for collection purposes and variety.

However, if you're asking questions about if BS is better on defense and seem serious about Snorlax defending and its utility, I think it's better for you to hold off, just because you really need to be oblivious to utility to be maxing something out that is not the best in the game.

I would not touch it at the moment because snorlax' moves are all worthless atm. If it ever gets a competitive charge move I would make this 100% a long term project, but not with the current movepool

keep them both, power up neither because you said you don't have a lot of dust.