A hit in Skeet is the same as in Trap. There must be "at least" a visible chip knocked off the bird. You will find many just "dust" remaining. Especially from station 8/9.
Most skeet (and trap) ranges don't like you to leave your shells on the ground. So if you opt for an 1100, you may need to stoop and pick up all your shells, which also adds to the time per station, especially of 2 or 3 also pick up shells. An O/U eliminates that, just catch your shells when you open it and put in your shell bag/vest.
A trap double can be used, but you will find it does not work well. Skeet guns are stocked more like a Field stock, a little lower drop at comb and heel, making for easier mounting (especially if the members shoot "traditional" skeet, starting with a low gun).
I had used 12 Ga SKB that worked pretty well, which I upgraded to a Browning Citori, Special Sporting Clays model which I still shoot, but also added a Browning Citori Lightning 20 Ga that I shoot even more. Just shot it yesterday, 20-30 MPH winds but that's fun, still broke 20.
This is all over about 25 years. I find I enjoy skeet more than trap. I do still shoot on a trap league team, The Geriatrics, In the early summer.