I would like to put in a good word for the hybrids since there is some criticism of them above, and thanks to Starboard for the effort in developing them.
I sail an RSX and Starboard Z-class against a boat fleet and the advantage they offer is that they are easier to sail in all directions because of the stability. They can be sailed with a smaller sail than a formula because they still works in light winds without plaining. This means that it makes racing more accessible to more people with less skill.
They are slower than most boats in very light winds but they pass more and more boats as the wind gets stronger. They allow you to carry larger sails than most longboards (for a given skill level). Like every different boat or board, they require their own techniques which are not well known because they haven't been so popular.
There is no perfect board for all conditions nor a perfect boat for all conditions. I am sure that the phantom and formula are faster in most conditions but I know my hybrids are easier to sail. I race against the next vessel in front of me so there is always a challenge and an opportunity to improve.
My advice to any one who wants to race is just pick one board and have fun learning how to sail it. There is no right answer. Hybrids may have not have won over a big market but the idea did and still does have merit.