Craig- It's all in the physics of it... and I'm no expert. Here's something to get it started. Long skinny wings and sails are more efficient at creating lift than short stubby ones. Biplanes and ketchs are less efficient than sailplanes and high aspect sloops for the same reasons. Also, a ketch has more rigging to add drag. That said, a lot of long distance cruisers still go with a ketch rig for the reasons you mentioned. The ketch rig also gives you lots of ways to balance your sailplan in various wind conditions. Cheap ketch tricks... backing down through a crowded anchorage using the mizzen for throttle and steering! (I've only done this on a yawl.)

Labor saving devices like roller furling and in mast furling can help a person deal with larger sails until something goes wrong. Jon Eisberg has quite a collection of stories about that from his various deliveries.

There's a start.

Oh yeah, ketchs look cool, but I'll stick with the single mast for my own boat!