Trying to organize these into "best to worst" categories is like trying to quantify beauty. Too many variables, too many biases, too many cultural issues, and too much simply can't be added up to make a concrete score.
Some are better than others at certain jobs. For instance, sinew can add weight to a bow that comes in a little light. Thin goat rawhide or antelope hide adds imperceptible weight but is unbreakable. Sinew, even with varnish over it, will suck water out of the atmosphere and lose it's best attributes quickly while rawhide soaks in the varnish and is nearly submersible. Boo is a bobbproof backing, but nearly impossible to mate on a stave bow without the use of powertools to plane everything dead flat.
It's best to list the good and bad points of all the backings you are intersted in and then compare it to the conditions you are going to carry your bow. I have one bow that I shoot in the yard that isn't even sanded out. It's been like that for years, covered with dirty handprints, grass stains, even some red wine stains. But it shoots on warm and dry summer days just fine, but being hickory it would be the last choice in the world to hunt Roosevelt elk in the rainforests of Washington state. Poor thing would drop from 50# draw weight to 8 lbs and stay bent at full draw until it got back home to South Dakota!
What conditions are you going to carry the bow you are interested in backing?
