While I favor H110 for the magnum trio,I can't find a single negative point about 2400.Yes,I think it is a little snappier than my favorite and gives up a few fps but one can do a lot worse than 2400.For my part,the few pounds I can find in my neck of the woods(altough supply has improved a lot these last 2 years)I save for my cast bullets rifle loads.
Since you said you don't need full power loads in your .357,I think Unique is your best bet.
IMR 4227,while an excellent one is,in my opinion too slow burning for such a small combustion chamber.The nice side of it is that it will fill the case and not create overly dangerous pressure and,as an aside,is extremely accurate in any handgun I've tried it in.