Thor and Loki are both shown to be extremely durable and fast. So is Palpatine (faster, not durable) when fighting Yoda. Not sure about who is faster. So who will hold up to getting hit? Thor will 1 shot Palpatine with the hammer. Possibly 1 shot with lighting, if not, it will hurt him and stun him badly. Now, will a light saber kill Thor? I don't think so. Burn him maybe, start to slowly pierce him maybe, but I don't believe it will cut his arm off or stab him fully. Even taking a few hits, he will get in a single hammer strike or multiple lightning strikes to take down Palpatine.
And concerning whether he can control his hammer midflight--I don't think it was shown really conclusively, but remember when he threw it at the Asgardian Destroyer who deflected it with the blaster, but then the Destroyer got nailed in the back or head when it returned back to Thor? It appeared to me that perhaps Thor was able to redirect it, at least to a degree. Just my opinion.
And with the stuff Thor was doing by slinging the hammer in a fast circle--making tornadoes and also using it to graze the ground on the frost giant planet and sent rock hurling at the opponents...he could use it as a large shield or offensive weapon or both at the same time, can fly up high and send lighting down, etc. He can do so much and is extremely hard to hurt. I see the majority going to Thor. I think Palpatine could get an occasional win with fast light saber attacks stunning and slicing Thor until maybe stabbing through the eye or something, maybe getting into his abdominal area...maybe.
Loki was able to easily catch Hawkeye's arrow without even looking in the direction it was coming from, and Thor fought him hand-to-hand. Loki was a stud too though--probably underrated. Thor should be able to at least take the beating Hulk gave Loki, plus a little more. Loki suffered no breaks or blood during that.