From my novice perspective I would say d then b. I would put b first, but I am a little concerned that the sumi is going to overwhelm that koi. I like d's hi pattern in terms of balance, though b is pretty close. I think the shiro on the face of d creates the possibility of some dramatic sumi and I like the tail tube on d better than on b, though I would like to see some shiro at the tailstop.
Buying for now I would pick, b, for the mud pond I would pick d.
Of course, I've only been at this since August so don't give any undue weight to my opinion.
