My opinion:
1) "Medium" sized piles are the way to go.
2) Refresh your productive piles when needed.
3) Really big piles usually produce large numbers of short fish, so you have to cull a lot.
4) Small piles produce small numbers, but occasionally big fish.
5) Good sized hardwood piles seem to produce bigger fish.
6) Rather than the size or type of piles, focus on LOCATION!
also bamboo and river cane is the worst thing you can use, next to pvc. a week after you put the bamboo out, all thats left is skinny, spiny sticks in a bucket. all the leaves fall off in a week, and that lush bamboo forest you envisioned that the crappie are playing tag in just doesnt exist. You may as well just go sink a five gallon bucket with nothing in it .
Hate to be contradictory on this one, but I can personally attest to bamboo condos I have out from several years ago that still produce to this day. In fact, we caught a 2 man limit off two Boo condos this past summer on Palestine, and they were put out 3 years ago. Yes, the leaves will fall off eventually, but the bamboo last a long time. Those same bamboo sticks are held upright by pvc, so there's another contradiction.
I agree that, if given the option, good solid hardwood limbs (or whole trees) are the way to go. But bamboo WILL work.
To me, the bottom line is put out what you can and be selective about location. Like LeaninPost said about Granger, too many piles in a given area can tend to scatter fish.