Snorlax question ^^

If you plan on using him for defence and don't have better ones by now, probably yes. If - as I'd suggest - you want to use him on the attack, he's already good for that.

Going from level 27 to 30 will take 24 candies and increase it's CP by about 250.

If you're going to set it as your buddy, 24 candies is 120 km. If that's worth it for you, power it up. Personally I wouldn't, not because it isn't worth powering up, but because I think it's already good enough as it is for attacking, and if you find a lower level Snorlax in the future, or hatch a Snorlax from an egg, you'd probably want to spend those 24 candies on that one instead.

I'm going to take a slightly different track and say that for me, the one thing I try to do is break up streaks in Gyms I want to hold for a while.

3 Vaperon's in a Row... drop a Snorlax in there.

2-3 Gyrados in a Row... drop a Rhydon in there.

etc. If the Gym game has lots of Vaperons around 2100-2500 range in a row in your Gyms, keep him and drop him in to break them up.

Good Level 30 Vaperon's though are 2600-2650. So if you need to power him up to that range go for it.

Power up and put him on Gyms.

It is probably around as effective attacker as perfect IV lick/eq (which is around 86% of perfect lick/hb, which is the best attacker according to qMike's sheet (TDO)). I think it is worth leveling up if you need a strong attacker.

As an attacker, he is fine as is and you should feel free to use him now and see how he performs. If you like attacking with him, powering him up may be worth it to you.

As a defender, it comes down to CP. At Level 30, his CP will be ~2600, which is very good but not fantastic (a higher IV Snorlax will be ~2800 at Level 30). How does this measure up for your playing area? The alternative is to start using him in gyms right away and see how he measures up.

Given that this is not a great moveset for defense (but it is great for attacking), you don't want to find yourself in a cycle where you feel like you need to keep powering him up to stay relevant in gym battles. If the moveset was ZH / HB, I would say go for it, no doubt.

Keep in mind that probabilities eventually even out and given how much you play (Level 34.5), I can see more Snorlax in the wild in your future...