From what I have read on many forums, 52100 was developed from 50100B (from 1095 etc)to provide a knife that would take and hold an exceptional edge. The move from 50100b to 52100 is described as a small step down in toughness and a step up in edge quaility. Super edges come from fine grain steel. Mike Stewart describes 52100 as a very fine grain equal to A2 and 12c27 (talking steel grain size not toughness). SR101 is an improvement over 52100 and hemce should be "known" for its scray sharp edges.
The whole subject is definitly a function of geometry and edge profile (these may actually be more important than steel).
All things being equal I would expect SR101 to take and hold an edge better than SR77, with SR77 being tougher. Several people on various forums have stated this from experience also.
My understanding is that INFI will take and hold a great edge also. Some of my Busse knives have been very sharp and some very dull (from the factory). The two Busse knives at the ends of the spectrum are my two SJTACs. Satin finished one Scarry sharp (I love that term) and my first Busse (CG SJTAK) someone forgot to sharpen.
Ron Athay