A few facts:-
As A diver since 18 (now 70) I have seen a fair amount of anchors on the bottom and my conclusion is a fixed shaft heavy pointed tip type anchor is the best for all types of bottom.
Swivel type anchors (like CQR) just run across the bottom surface and do not as a rule dig in, only on soft bottoms like mud do they perform well, or like NJSAIL CQR twice the weight needed. Remember the anchor holds the chain not the boat, so enough chain out is critical. You could throw a concrete block over as long as the chain is long enough to support the conditions.
For personal reasons and local conditions (France hard sand strong tides) I have a 20 kilo Kobra 2 on a Bav 38 and it digs in immediately. However getting it out you have to run over it.
I also have a Australian "Flying anchor" looks a bit like a stingray fish used for winching off sideways, hits the water and goes down at 45 degrees , hence the name flying anchor.
Hope this helps
Odysseus