This is not always true.

A few exceptions that favour the slow cats are increasing winds during the race, a persistant windshift in the last part of the race, windconditions that are to low to properly fill a spinnaker, very big winds.

Afterall this year at round Texel a 20 year old Prindle 15 ended up 2nd overall, only 35 seconds from winning this years round.

The advantages/disadvantages work both ways. But most often you see the modern boats win out as typically these are sailed by more serious racers, while the oldies/slow boats usual have some recreational crews on them that do a event only ones or twice a year.

Wouter