I've used recent S-Type and GTX in large sizes. My impressions are not scientific but the GTX 10.5m was beautiful to use, and my favourite. Tushingham Lighting is very nice too. My V8 is an earlier edition so perhaps not fair to say it doesn't quite match up, feeling 'heavier' in use. It's actually pretty heavy on the scales too, and the static weight is something you certainly notice trying any of the full race sails after the best freeracers. Interesting Maui do a special light version, didn't know that, at least they own up to the 8.4kg weight of their standard 12.- Many brands don't quote a weight, which when you think for example of the emphasis placed on mast weight, is crazy. I do know Aerotech can do a Pentex version of their VMG, and user feedback is that it makes a real difference.
Seems like most riders don't want to bother with this big kit, and I've gotta admit theres a case sticking to freestyle practice when it's light. But skimming effortless over the flat water at a windspeed multiple, and making the use of every little puff to work upwind is absorbing and satisfying to me.