I've owned the first two!
I already talked about the S3, and in terms of the GT750 it's now a cult bike so worth much more than the others.
My second one threw me off at 110mph with a tankslapper in 1978 so my memories are painful ones.
Besides that they're pretty quick, fairly thirsty, and ground clearance is a bit limited.
Having said that, I'd still choose that one over the other two.