Upair aerial interrupt shifts your ECB downward so that you autocancel before the move comes out, and you snap to the platform well before you'd usually be able to land (i.e. you land while still rising). You end up with the standard 4 frames of autocancel landing lag.
Missile canceling on a platform, done correctly, causes a no-impact land. I believe shooting the missile causes the ECB to shift upward, so you can sometimes make the platform when you ordinarily wouldn't be able to (e.g. shorthop homing missile on Battlefield). You still have to jump all the way to the platform, which puts you on the platform slower than an aerial interrupt does, but you only have 1 frame of no-impact land landing lag.
The former is faster for putting yourself in an actionable state on the platform. The latter puts out a missile (and in fact you can usually no-impact land even without firing the missile, except in my earlier example of sh homing missile on BF), but you land on the platform later.