I have been sailing my phantom 320 for a full season (last 9 months) against dinghies. I have found that the 320 gets steadily faster relative to the boats as the wind increases, with a big jump in speed once you get planing. The boats that have huge spinikers are always hard to catch since I am limited to the one sail down wind.
I was mostly the only sailboard in the race, but on the odd occasion I had competition from more experienced sailboarders on mistral equipe or superlite, they have always gone faster than me. Obviously my skill level is a major factor. (my 4 years against their 20)
anyway my personal opinion is that the new raceboards don't offer any quantum leap in performance. They may offer a noticeable advantage in a sailboard fleet but if you are racing against boats, I don't think you will benefit much.
I think the extra width in the 320 makes it easier to sail downwind and gives it better general stability. this is agreat asset for a less experienced sailor like me.
I'm not sure since I have only had a short trial of an equipe but I have felt that the 320 seems to do a better upwind angle. I can do close to 100 degrees tack to tack (measured on GPS)in all but the lightest conditions. I can point at least as high as the boats most of the time and often higher and faster than some of them. It is always difficult to work out the cost benefit of the hight vs speed.
Sailboards Vs boats is realy not a fair contest since their performance parameters change so much over the wind range (as ken pointed out). Do you really want to replace your board just to beat a boat?
If your old board needs replacing and you don't mind the cost of a new board, then I think the new models are worthwhile. Otherwise, My preference is to spend money on new sails that are improving in power handling and wind range every year.