Current Darkseid loses, obviously. Post Crisis Darkseid before he got butchered has enough feats to make it a fight and then some (He easily captured Superman and Infinity Man with some Omega's, for one, and the Omega's were shown as ignoring obstacles and acting intelligently, as well as capable or traveling through time and space..)
And for the hell of it, some opinions on PC Seid:
Darkseid from The Great Darkness Saga obviously wins.
Original Kirby Darkseid may win or lose depending on whether he tries facing Thor down mano y mano, or if he fights cheap. He took down Infinity Man with the cheapness, Boom Toobing right behind him and hitting him with the full OE before he could respond. And, the OE cleaned up the Forever People, tracking them down and sending them through time.
However, this version of Seid also has zero combat feats, and in fact ran from direct confrontation with his son, Darkseid. So likely, Thor beats Kirby 'Seid down.
That said, Kirby Darkseid is bigger then mere wins and losses. He's, by far, the coolest Darkseid ever.
One of my favorite Kirby Darkseid moments: