To have an idea about the relative performance of two sailboats there are few things better than a good handicap list. The more reliable are the ones from ORC but there are others that provide good information, the problem is that they are not many times compatible and some times it is hard to find information specially in what regards older boats.
Blur has some great information regarding handicaps and I find this one specially good. They are IRC handicaps and the newer boats are not there but lot's of older boats including American ones. It is a very interesting one since it can be provided taking into consideration only speed and that gives an easier reading in what concerns other comparable sailboats and also by alphabetic order.
Regarding the one that is ordered by speed we can pick for instance a famous relatively fast and very popular old American sailboat, the Cal 40 (0.964) and take a look at boats with similar performance:
It is surrounded by First 31.7, and Elan 31 and 333 but it is slightly faster than a Catalina 38 or a Jeanneau 37 with a swallow draft and about as fast as a Morris 46.
That is kind of amusing to see what a given boat compares in performance.
Here you can see that same list but by alphabetical order.
Another good place to find information about the performance of more modern boats is the site of the FFA. They use different ratings and apparently they seem directly comparable with ORC numbers but they are not (unless converted), so in fact they are only comparable with themselves:
Federation Francaise de Voile