I voted Mountcastle. With SSS it's hard to say definitively, however I've seen Trey play a decent amount of 1b and he's never stood out as being anything more than average. I watched Mountcastle a bit in minors and thought he was a decent fielder, very athletic, but had a poor throwing arm. I'm assuming long term that athleticism translates to 1b, but he has looked a bit shaky there this year learning a new position. When it's a toss up, I go with the talent over the polish.