Stick to full grain or top grain.
Full grain is the full hide, this is the good stuff, the most durable and will be top price.
Top grain is almost the same, but has the top layer sanded off to remove blemishes. After sanding, the surface is imprinted with a imitation grain. You gain uniformity, but lose some of the strongest fibers (and character).
Tom's Leatherworking pages / tom@mmto.org