I do much the same thing on an informal basis, without keeping a detailed record.
Its worth watching the boats anchor if possible. The amount of reverse will effect the depth of set. Its also instructive watching which boats drag (if their scope is OK). If you want some real entertainment watch the anchors rotate in strong wind.
My own observations very much mirror yours, although I would rate the Spade as slightly, and only slightly lower. it seems to struggle in weed and softer bottoms a bit more. Also the aluminum Spade is not as good as the steel one so it is probably worth separating the two materials in your analysis.
I have also noted the Delta while it normally sets well it can slowly drag under the surface even when completely buried. (it looks like a burrowing worm)
There are lots of other anchors that are popular in the Med Kobra, Brittany Fortress , bugel etc. Did you gather any data on these?