[Rune Son of Bjarne]

On all accounts this is a difficult question to answer, because what kind of combat are we talking about?

Are they fighting with no weaponry and armour? If they do have weapons, what kind and is it in some sort of arena or in random terrain?

All of these things matter in a fight, not to mention strength and wits. . .the sad thing is we can only guess and not even very qualified. At least I cannot.

Yes the elves killed Balrogs and the dwarf died without killing the dragon, but we do not really know the specific sercumstances for these killings. Who knows, maybe Glorfindel was very lucky and Azaghal very unlucky?

Personally I think that the elves would win, they just seem to have more strenghts than the dwarves. Maybe the dwarves could carry heavier armour, but I doubt that would win them the combat.