Honestly, I have to agree with those who said G0-T0. Revan and Grievous would be mashing against each other pretty good and while G0-T0 would be destroyed in a fair fight against either of them I think Revan and Grievous would be working against each other. Revan might want to take Go-T0 out first, but I doubt Grievous would give him the chance. Regardless which side won against the two of them, Grievous would have quantity advantage while Revan's forces had more quality, whoever surivived would be an a position for a droid revolution and exchange sab teams. If Revan beat Grievous, he'd be vulnerable to his fleet turning against him and bombing him (as well as the risk of Malek turning on him which isn't all that unlikely
). If Grievous won against Revan then he is royally in trouble because a droid revolt takes out pretty much all his forces and I doubt Grievous would be able to run and hide from G0T0.