TOTALLY AGREE WITH YOU.Marco would win.
Marco's healing ability, Haki, Close Combat skills would give him the advantage in close range.
If it's Long Range, we saw his closing speed.
Marco was stated by the Gorosei that he's strong enough or one of the few that can bring down Blackbeard.
Adding a little logic and some imagination, Teach can most likely defeat Sakazuki, Kuzan and Borsalino in a 1 on 1... agree?
If Marco is capable of bringing down someone of that caliber(Teach), it's probably best to say he can defeat those 3 in a 1 on 1... agree?
Now subtracting my little logic and imagination, I can conclude that because of Marco's Haki, Flames and superior Close Range Speed/Skills he is capable of defeating Borsalino.
*Remember when he had full concentration/focus in his 1 on 1 fights, he was able to wreck Borsalino, Kuzan and to a certain extent Sakazuki.
I have nothing more to add except there isnt a limit to he´s healing power. He automaticlly regenerates. Only question is has he haoshoku haki( King´s haki)?