Quite a lot of this is subjective though, opinions on the same brake vary due to set up.
Brakes I've used for DH:
Saints (810), was a little disappointed, expected something special after hype, good solid stoppers though
Tech M4, great for most DH, but I found that they seemed to fade more than others on longer descents. If they were set up anything less than perfect I found them to be a little underpowered for DH
V2s - mental. Can't imagine needing more brake. Mine had a tendency to make lots of noise
Codes - worst brake I've ever used (I've had 2 sets), didn't like setting up or bleeding, one lever fell to bits on a descent and another caliper seized. I found them to be quite wooden
SLX - surprisingly good, not far off the Saints I had and a nice feel to them, I'd happily run SLX or XT on a big bike again, great value
NB - I run dinner plates