Silicon seals have some important advantages over traditional latex seals. They are extremely flexible so easier to take on and of, increased comfort when wearing, one size fits a wide range of wrists. Great material stability so better against ageing, UV light and chemical degradation. More resistant against puncture. Better for allergies. Less friction (antifriction coat on the inside).
There main disadvantage is the problems with gluing them to drysuits, this is overcome by using neck and wrist ring systems, the best of these coming from Sitech.