If we are talking the manga then my vote goes to Koan since she wiped the floor with Mars, while Mars had the upper hand on Eudial landing the only attack of their encounter. Although I guess revived Eudial I guess technically won with her pure head game to trap Mars.
If we are talking the 90s anime then Eudial hands down. I mean come on she freaking cancelled Moon Spiral Heart Attack with her Fire Buster. Even Mars is going to have a heck of a time matching that kind of raw power. Koan on the other hand had nothing on that level being in bad shape after a single Burning Madala attack...
Let's not forget that in manga, even though Mars landed an attack on Eudial, it didn't kill her, but turned her into a scary monster.