I'm at Omni, have a bunch of friends at LCCs. I would guess that for the majority of guys, maybe 70%, the LCCs are a slightly more attractive option. Obviously, as with all things, it depends on personal preferences. I'm single and childless, so being gone for long stretches is no great hardship, and I enjoy travelling the world. I do have apps out, but at this point, I would only make the jump to two or maybe three carriers. And that window is closing as I accrue seniority here. If we weren't owned by ATSG, it might have already closed, but I just can't find enough confidence that they won't find a way to screw up a good thing to give up quite yet.
I should add that Omni is a bit different from the other ACMIs, as far as I can tell. We fly a lot less and we get 117 rest, so this is a great job if you're kinda lazy. Of course, because we fly less, we also make less than guys at Kalitta, for example, with similar seniority.
The guys who seem happiest at LCCs seem to me to be either committed short-haul guys who can't sit still for a 12 hour trip or guys with families, which only seems reasonable.