It depends on your shooting form with both. If you use a straighter wrist position and a straighter bow arm with a recurve than you do with a longbow - and most people do - then your draw length will be longer with the recurve.

The distance from the shallowest part of the grip to the back of the bow (or length of the shelf, as you describe it) has nothing to do with draw length, at least by the AMO/ATA method. It definitely determines how long your arrows must be but that's about it.