Well, the big advantage of a:B+K is that it has good range. Imcf has poor range so situations where it can be performed start just announcing themselves in your brain when you play against a good Yoshi. This doesn't make imcf useless at all but fast as it is the range requirement means that it's often can't be as much of a total surprise as you want (note this is my experience playing against Yoshi rather than with as I can't do imcf consistently). However a:B+K can be a total surprise. Vs Voldo, yeah if he's whoring A+B and 1[K] I wouldn't use it but sooner or later Voldo will want to throw out 2A+B and that move is slow and I don't think it TC's until maybe very late if at all, so it should be vulnerable to a:B+K.