High speed is more picky about soil conditions if it is dry on top it will not go into the ground. More N is lost during application, can tell this by seeing and smelling, although I am not sure if it is enough to matter as I have raised 172 bu corn from 127 lb N applied with a high speed DMR/crustbuster unit.  I have only used it preplant and normally go at an angle to corn rows.  Soil erosion is less than with a knife even when comparing 15" spacing on high speed vs 30" on knife.