Power Up Legacy Low level Snax and Nite

The IV distribution is especially important for Snorlax IMO. If it's a 15/15/2 Snorlax you have, it's a nobrainer. I powered a 71% ZH/BS Snorlax with 15/8/9 from lvl 9 to lvl30+ and I don't regret it. If it's a 2/15/15 though, I'd probably hold off. The reason being that attack IV counts double in CP calculation and that Snorlax already has 320 base stamina.

For the Dragonite I'd put emphasis on high Stamina and Attack IV. In this case, I'd look at the options and your attacking style. I have a feeling I'd rather try my luck at getting a DT/O or DT/H attacker, than powering up a low lvl Dragonite like yours. If you already have another DB/DC Dragonite, you probably won't need it anyway.

Dragonite, do you have another? Maybe useful when trading comes. Otherwise, DT/Outrage performs better in most cases.

Snorlax, do you have another? ZH/HB and ZH/HS are also decent. 71% IV may be too low.

I would power them both up. I powered up a 60% Db/dc Dragonite.

The lax is a no-brainer. That is the best defensive move set and it is legacy. Power him.
I like DB for, attacking. Since DB is legacy on dragonite, I would power him as a generalist attacker.

If it's for gyms, I'd wait on both...To me, CP is still king and 71% is too low considering I'm in a Rhydon biome who has near Snorlax CP...

I think moves are overemphasized for defenders and as powerful as a 2900CP ZH/BS Snorlax is, my Lvl 25 C/CC Machamp can wreck it in 50 secs.

I only dislike Blisseys due to time needed...and high possibility of timeout if you have lag or dodge bug/swap issues.

I have a very similar dilemma, just my Snorlax is 872 and my level 1 Dragonite is DT/O.
My decision for now is to wait. Niantic already said the gym battle system is gonna be reworked, so I'd not use that much dust and candy by now.

I already have powered up to level 30 a DB/DC dragonite with lower IVs with no regrets. DB fits my style of attacking, so I have lots of fun with that 'nite.
I have also already powered up to level 30 a ZH/BS snorlax with lower IVs as well. No regrets.

those are both fine mons and will be very happy at level 30.
as far ar "an beyond" goes:
I have not power up my 'nite higher because at level 30 the attacking good enough to me.
The lax is already high enough to sit in gyms at level 30. If you need him to sit higher then take him beyond 30.