Though the Mass Effect series is full of interesting characters, it’s widely accepted that Tali is the best of Shepard’s companions. She is also the best romance option hands down. I have played Mass Effect several times and I always romance her. Regardless of whether I’m renegade or paragon. I even installed a mod to romance her as femshep during one of my runs. I’ll fight anybody on this.
Yeah, Tali and Legion are the best choices for the vents, but towards the final fight she and Mordin are high in the priority list to die if left to hold the line and you don’t have a strong enough defence. I made that mistake on my first playthrough of ME2, taking Garrus and Tali to the final fight (taking one of the strongest defending characters from the defence), thus Mordin died at the end. That involved a reload and a replay of that mission so I could have him in ME3 lol