Tough question.
I'd want someone who didn't talk a lot. Unless it's to point out a nice, thick ass on a girl I might not speak at all during a work-out. There are a few people there I hang with in normal life but I'm there to work out, not talk.
I'd probably pick Div, because he gets my humor. Maybe Sarcasm or a few of the guys from The Squad to blast the crap out of legs.
Arvilla would be in front of the mirror or on his cell phone too much, LOL!
Alexxx doesn't look like he could spot a 16yr old.