I like a prime Liston to beat Ike. Ike was a talented fighter but prime Liston with that jab was a tall order. I like Holyfield's combination punching and pure athleticism to win out over the hard punching but limited Tua. I believe there is some sparring footage of Tua and Holyfield out there.
Tua reportedly did well against Holy in sparring. But sparring is sparring. Tua didn't have the intangibles to beat Holy on the big stage.