Let me take a run at ranking cat classes. (since I can't sleep anyway)

1. A-Cat - Due to depth of skill and number of sailors
2. Tornado - The top teams are Pros- no #'s
3. H16 - The shear number of sailors and events breed great racers. Don't knock it until you've tried it.
4. F18
5. Hobie Tiger-more #'s & depth than both N20 & Nacra F18
6. Nacra F18-Great skill at the top, but not the depth of the Tiger Fleet
7.N20-Usually the same players as the Nacra F18 Fleet, just not as many boats
8. N17
9. Wave-Boarders on being a regional niche boat

The rest are niche boats. I think anyone who has gotten in to the top 5 in any of the above could make a pretty serious run at winning those classes. The old Hobie classes still have their die hards and specialists, but their appeal of the boat for whatever reason, takes away from their participation, thus the depth of the fleet.
H20
H17
H14
Not really sure about what order to put the old Hobies in, but I do know that the venerable 14 is staging quite a comeback on the National level

Isotope
Shark
N6.0
these three classes are really only raced regionally, so the numbers of participants is low.

I also do not like seperating out individual F18 manufacturer classes. Hopefully that will go away in the not too distant future.

Disclaimer: My opinions can change with reasonable discussion &/or enough rum <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />