What do you think about them? I am riding dressage and wonder if it will fit my Arab. I don't like bulkiness and their Nexus model looks the smallest.
What do you think about their concept of saddling?

A saddle is a very personal item and once you find one you like thats what you stick with. As for your horse I've had success with these on Arabs;
Windsor greenline
Lovatt & Ricketts
Jaguar
I have also ridden them in Crosby,Kieffer,Courbette,Prestwick and Harry Dabbs
But found the above 3 had an overall better fit.