So I've got a question for the Fan Club.
Who's faster?
VS
My two cents: My belief is that when Rainbow pulls off the Sonic Rainboom, she is going supersonic (Mach 1), however, that doesn't mean that's the fastest she can fly.
The SR-71 has been known to reach Mach 3+
I believe Rainbow can reach Mach 4 if she pushes herself enough.