52100 vs D2 is almost an apples vs oranges situation. 52100 is a low alloy steel that can achieve very high hardness(Rc66-67), very fine grain, and a simple heat treat(even with normalization, should be less than an hour to start first temper cycle, cyro not necessary). D2 was formulated to produce large amounts of carbides that will make sharpening and polishing a pita. heat treat takes longer and should include cryo for best performance.