Which one of these do I evolve into Tyranitar?

lv34 one looks more promising due to lvl and better attack and defense, however if you are not in dire need might want to wait like 2 weeks for announcement , larvitar might become new community day pokemon

I'd do the level 34. Adventure week might bring you some additional wild larvitar, too. When you find them they can be boosted since clear + partly cloudy happens a lot

Yes, wait until after adventure week is over. Your chances of getting a better candidate then are pretty good. And of course, there might be some new research tasks (aside from the three excellent throws in a row, which is a pretty steep challenge for most trainers) to get Larvitar.

If Larvitar becomes a community day pokemon, it won't be until June, and I suspect later - the usual pattern seems to be to spread out the ones with meta-relevance. Pikachu, Dratini, Venusaur, Mareep, Charizard. If I had to hazard a guess for June, I'd pick Squirtle, to complete the gen1 starters. I do think Larvitar will be a community day special, but not for a while. I wonder whether Ttar will get a special fast rock move, or a better dark move as the evolve special. So trainers should save up a few good Larvitar or Pupitar for that day, knowing it might be as far off as 2019, but when it comes, you'll want to be ready to get a pokemon that is unobtainable any other way.

you could try to just get into a Ttar raid and save the candy.

I don't see how Pupitar saves you any candy, the 25 you save would not be anywhere close to getting you up to that level 34 Larvitar.

I don't see anything wrong with evolving L34 one, it's 3300 ttar ready to use. IVs are pretty solid, 15att. 9 stamina is only 5 hp less at level 34 and only 4 at 40.
L20->34 is 114 candies AND 123k Stardust. L25 is only 86 candies, but still 92k Stardust. So even powering up raided ttar will not save you a lot of resources.