They don't point as well, either. Generally, pointing ability goes this way: sloop, cutter, ketch, schooner. That's why you'll see ketches (when you do see them) on passage rather than racing around the buoys).
I like ketches a lot, but they are specialized equipment. A sloop is more generalized. On a reach in a tradewind, I'll take the ketch...it will likely be faster if all else is equal because it can set a great deal more sail. If you've ever seen a ketch with a fisherman's, a mizzen staysail and all other sail set, you'll see why it's liable to outrun a sloop.
Ah, here's one: A big ketch with furled staysail and
jib, but with Code Zero, full main and mizzen and mizzen staysail (you can also fly a mizzen
spinnaker)
