The first call to make is whether you like RACING solo or with a partner. The racing experience is very different and both are fun in different ways. The team aspect of getting the boat to move is a lot of fun as is the private experience of a solo boat flying upwind or down. (if you go solo... make sure you buy beer for your friends with a sloop boat... crewing is still fun as well)

The next big decision is whether you RACE solo with a chute or not. Since you only have two hands... racing a spin boat shifts your attention slightly. You have to get the boat around the corners first and then worry about the fleet. The simpler A cat allows you to race your competitors around the corner a lot more aggressively.

Another factor is the length of the race course that prevails in your area. A short race course will get old fast with a spin boat... (one or two man).

Finally, if you want to race today... it comes down to what is popular in your area right now. Growing a fleet is slow and unpredictable. You rarely see a region with equal numbers in the classes.

Bob Hodges had a great description of the two forms of racing... but I just can't remember it..