You will want one that is as big as you can handle and is accepted in your class.
And one small enough to be used on those days when it is blowing stink and boats are just trying to finish with out capsizing.
John's right. I raced in our C34 one design (all year) fleet from 1998 (started in the Kurt Zane Memorial Trophy Race run by the C30 skippers) until 2006 (quit while I was ahead!!!
). Our class max was a 130, but many times in windy conditions I beat others with 130s with my 110. Even on the old reaching courses from Blackaller to Harding and then to Ft. Mason.
We eventually split into a racing and cruising fleet for our C34s, but most of the year was our own starts in the Midwinters and GGYC summer series, finally the SBYC. Everybody for themselves in the Rites of Spring Race. I never did the 3 Bridge Fiasco.
I found practicing the course during the week really helped. Even my "cruising" The Bay helped, 'cuz either you're sailing your boat properly with your sails or you're just a goof! "It's a sailboat, stupid, sail it right."
Having most of the courses using the buoys helps, but I was also around back when they still used the Berkeley yellow marks, most of which went missing after a few winter storms!!!
Now that I live here, I'm a "trawler with a stick!"
My advice? Go out and practice. It's like docking!