White and black bamboo is from under the ground (root bamboo) and will have the knobby nodes traditionally seen in bamboo shanks. Root bamboo will always have a slight curve, and if requested, I can pick out very curved ones.
Buddha belly bamboo is from above the ground and has smooth knuckles. Pieces will vary in straight sides or bulby sides. Buddha bamboo is typically straight.
Seconds are available at a cheaper price. Seconds will have discoloration, or odd sizes, and will have knuckles far apart and/or cracks.