Hull City are 2-0 down after losing the first leg and they will need to attack strongly to have a chance of reaching the League Cup final. United will fare better against teams that come out attack as Hull's defense will be exposed to United's counterattack. Furthermore, United has won 12 of 13 games against Hull in all competitions. My bet is United -1 as there is a good chance United will win big.
Hull have some chance to get something from this game. They defeated Bournemouth by 3-1 and have a system that is working, even with all their limitations, and Manchester United already have a 2 goals lead entering this game.
For me will be a defensive game with few goals, so my be would be in under goals