OK, a bit of an update for anyone still interested. 
I picked up a Ranger S head today. In a bizarre case of cosmic coincidence, the box which the dealer pulled off the shelf contained my S head - the "A" was crossed out and the "S" penciled in, and he remembers doing that when he pulled an A head off the shelf to make up the A kit for me (he didn't have any A kits left at the time, only S kits, so he made one up for me
).
There are some differences between the two heads. The flashtube inside the Ranger S head is the regular Omega flashtube, similar in looks to what is inside the RX strobes:
At full power the S head does not sound like a rifle shot, like the A head does, it has a more gentle pop, but one that still gets your attention. You know it's 1100Ws going off!

The sad news is that the max sync is 1/3 of a stop slower than with the A head, and this is with both my cameras, the 5D and the 1D mark II N. To keep the comparison fair, I used the same equipment as last time (Skyport RX trigger). So it appears that it is the fast flash duration of the A head that makes the difference!
So, that's about all I know right now. I will likely use the S head for most of my work, unless I need the fast flash duration of the A head. Only time will tell if I end up with two or more heads of the same type.
Here it is. First time I've used my Deep Octa as a background!

All photos of the Ranger S head were lit using the A head in the other port.
