I generally use 4140 or H13....but honestly, it's not going to matter if you're cutting feather pattern with a press...nothing will hold up to the heat and pressure. Well, let me rephrase that.....nothing that I can afford will hold up!
I'm sure some of the "super" alloys might....but a piece the size needed for a hot cut would make you faint!
I'm lucky enough to have a friend who works on heavy equipment, and he brings me dozer cutting edges and such.....I always count on a cutter used for feather pattern to only be good for one or two billets....then I build a new cutter for the next.