Kojak are not comfortable, aren't fast tires and are fragile, I definitely wouldn't recommend those tires.

The R11 comes with a 11-28 cassette so less low gear than the GT.

The only advantage is the 11s transmission and Hubsmith wheels for which there should exist a XDR hub body (the problem is where to find it outside Asia, I never saw it sold online) allowing 10-42 cassette for instance.

But the price difference is quite big. The chance to find a sale for the R11 seems to me low, there weren't so many R11 built.