Aqualung vs environmental resistance?

[Cato]

a question that has likely been asked before -

Anyway Im used to playing the PS2 version of this game which has a slightly different map

- ive also not found a repair bot yet

[briarroot]

It really doesn't matter. You won't put yourself in a bind regardless of your choice.

You will find ample Re-breathers to help you explore certain underwater sections. Likewise there are a lot of Hazmat suits around to help you should you need one.

[ULTRA]

IMO you should do environmental resistance if you're doing melee or nonlethal because it makes it a little less costly to use gas grenades, but yeah, otherwise it doesn't really matter

[Danny Dark Soul]

Neither is particularly amazing, but Aqualung requires no upgrades to be useful. Tier 1 of environmental resistance barely helps.
Either way, you won't be upgrading either. There are more useful augmentations.