Is breaking bad with Contreras worth it? It seems he may be one of the best vendors around. I noticed he had thousands of 12.7 mm rounds and loads of caps. How expanded and diverse does his inventory get after this quest line?

Also, I haven't tried out Bozar since my inaugural run. How's it?

I think he's bugged and offers you the expanded inventory right away. Also, his quest is very buggy and prone to just not working.

Bozar is also a novelty. Strengths of neither, weaknesses of both.

That Contreras quest glitches for me every time. Eventually I can't get any more dialog out of him or the others you talk to during it. So I usually just turn him in.

I found the Bozar to be meh. And very expensive.

Turn him in and get a sweet battle rifle for your troubles.

His quest is glitchy but getting it to work makes him one of the best vendors in the game imo

By Bozar you must mean This Machine? I've heard it's very good, I've never used it myself (I sold it with my last character) - you get it from siding with Boyd anyway though. I found that after his quest he did have significantly higher amounts of ammo (literally all the sniper rifle ammo you could ever want) and he's also the only way to get Ultra Jet (which has permanent addiction) so I think he's worthwhile to keep around.