What I do know.
H-1 is rust proof, X15 T.N. is not.
Other than that I can only speculate.
IIRC X15 T.N. should resist rust very well, better than your average 420j2 (which is pretty good).
Going by the information on the alloy chart it should hold an edge about as well as H-1, maybe a little better at first (before H-1 work hardens).