Belt vs shaft is no longer an argument. Yes-they perform differently out of the corners-but it affects handling more than sheer grunt. Also-how long the shaft drive drivetrain can spin is no longer a valid argument for on track performance. I would even argue that hogged out tranny cases and poorly set gear lash that leads to a super fast and long spinning drivetrain in the pits are disdvantageous on the track at times.
For example-my RDX drivetrian is smooth-but far from free spinning-yet it looks to me like it accelerates with any car on the track.