I am in/through Malmo a few times a year and I can say that it's a boring place on Sunday and thus recommend staying away from there on Sunday. Other days of the week it is fine. A one day trip is nice and if you want you can stay at the Hilton Malmo (but it's quite a hike from the train station). [There are some Scandic hotels there too which can be had for 10,000 HHonors points.] Malmo is not an ultra-vibrant place but a day trip to walk around is nice and pleasant. I remind you of a comment I remember reading about here on FT: "Sweden is boring outside of Stockholm." [I can say I don't necessarily agree with that comment.]