I always use planar map. It is the standard most poser maps use. I believe it's the format recommended in the directions too. If you are trying to generate a uv template of somthing that's already mapped and not trying to change the object's mapping it's the one to try first. Second most frequent is by group.

"Your work is to keep cranking the flywheel that turns the gears that spin the belt in the engine of belief that keeps you and your desk in midair."

Annie Dillard