It's nice to have this problem because they're talented. They gotta go somewhere.
I'd use Wells primarily in mid-to-long relief because the Orioles need somebody like that.Their bullpen is mostly 1-inning guys, and w/burn out quickly if they have a couple of starters knocked out early. Wells can give you 3-4 strong innings. He could also be an alternate closer in order to save the arm of our primary guy. And, he's done it before.
I like Hall as a reliever because he can fan people in pressure spots (ghost runner situations come to mind in particular). But he also walks them, so I'm leery of using him in high-leverage situations. He fanned 70 in 49 innings at Norfolk last year-but walked 30 (he did pitch better in his brief Baltimore stint). THEREFORE, I think they s./try him as a starter, first 1) to get the most out of his immense talents and 2) A few early-inning walks may not be as damaging-or fatal- as they would in a 9th inning save appearance.
If they can't get a good starter this winter, try Hall instead of signing some hack.