Bob,
In this size range there's almost no good reason to ketch- or yawl-
rig a boat. Unless you have a particularly low bridge to get under, or some other infirmity that requires small sails. Sure it was done a fair bit in earlier times, even extending into the early fibreglass era, but there are good reasons you don't see it done anymore on boats in this size range.
Generally with modern sail handling conveniences (furlers, self tailing
winches, etc) the larger relative sail sizes on a sloop of this size are still easily managed. Also, mizzen masts and sail handling tend to intrude on the cockpit area in undesirable ways. Add to that the extra cost associated with equipping and maintaining two masts and their
rigs, and most folks prefer the sloop or cutter.
As boats get larger, a better argument can be made in favor of ketch rigs for keeping bridge clearances lower and simplifying sailhandling.