Its probably so close that it might even come down to the fighters you root for or stylistically prefer. Cheers! Go Chad!
To me is: 1. Tito (he beat Oscar) 2. Shane (he beat Oscar twice) 3. Oscar I would've love to see Shane vs Tito but it never happened. I basically rank Tito above Oscar all the way because to me Tito never ducked anyone. He always wanted to fight the best no matter how risky it was.
This is gonna sound really dumb, but to me it makes sense. Although Oscar lost to both, I still rank him higher head to head. I think out of the three Oscar, in his prime, was the hardest to beat. Shane beat him fare and square which is why I rate that accomplishment so high. Tito got the "w", but he certainly did not "beat" him. Lets put it this way; If you take 5 fighters of different styles and make each one fight all three, I think Oscar would fare the best.
A bad stylistic matchup for Shane is someone with a punishing jab and size advantage. Tito didnt really have that. Shane/Tito/Oscar are always going to be close fights.
Shane and Oscar split a win each in reality, DLH clearly beat Shane in the 2nd fight. He beat Tito too. But SMM won the 1st DLH clash brilliantly. Like the Pac/MAB/Morales/JMM conundrum, this is a difficult question.