Here is a story, I hope its not too long. I used to be in motorcycles. There was a gentleman at a dealer one day bragging about his new Z1000 (this was years ago). It just so happens that a manufacturers rep was there. Naturally a challenge was thrown down. The rep took a bike of almost equal size (a few cc's smaller even) and they took to the road. Well the rep blew the Z1000 away. Then he suggested they switch bikes. He beat him again!! So the moral of this story is and it has been proven again and again, each boats potential is determined by its occupants skill. Thats why in a mixed race you will almost always see some of the "smaller" boats beating the 20's boat for boat. Its not that the boat is faster, its who can make it go fast.
So, my suggestion is fwiw, get something you like and learn to sail it as best you can. Most of all, have fun. Otherwise its like a job you despise, you won't want to go there anymore.

Peace and fair winds,
Clayton
S27 (size does matter!) I can carry more beer!