Utter boredom as it devolves into rolling dice to decide the winner.
Exactly this, and I believe it's very telling about what such a list offers to the game. It's actually more boring than watching two Fat Han lists face each other, so I suppose that's some sort of accomplishment.
Have you ever watched a TIE Swarm vs TIE Swarm. That is just as, if not more, a dice dependent matchup. At least with the Y-wings, things are likely to be removed in a timely fashion. And maneuvering does play a big part in that.
Swarm movement is way more important than y-wing movement when spamming tlt, aslong as your not in range one your getting a shot.
Given both sides are likely to be zipping around at speed three carparks are unlikely as is never getting a shot.
So as other's have said it'll probably come down to who gets priority.