Best raw converter for the D800 is...

I think that for this type of shot both LR and DxO can produce excellent results.

To illustrate the difference between LR and DxO we would need some high ISO shots or people shots or better yet high ISO people shots.  In high ISO shots DxO v7 would remove the grain from a wood floor and the pattern from a dress (at default settings). I think the defaults were somewhat improved in v8.