The Dodgers have 3 OFs under long term contracts and 2 studs on cheap deals right now, and some potential studs in the pipeline. They have too many outfielders. Kemp is practically untradeable given his contract, so he can be had for next to nothing in terms of prospects. He's an above average player, but very overpaid, and he's a CF. I think in LF, he's an above average defender, or at the worst, average. Etheir is also under contract, but he's not good anymore (though he is cheaper). I don't think the Dodgers will be able to trade him, and I'd be disappointed if the Twins targeted him. I wouldn't mind getting Pederson, but the big difference here is that he WILL cost the Twins quite a bit in terms of prospects, where a guy like Kemp can bridge the gap and not cost the farm a thing (just the Pohlads).
For those reasons, I think that if the Twins can afford it, I'd get Kemp. Not saying I wouldn't be OK with Tomas. My concern with Tomas though is that he's going to cost close to the same (though he'll come with a couple more years) and his defense is questionable. Like others said, he's a prospect. Not a bad get, and he could be an anchor for quite some time, but there's more risk here for what will likely be the same price.