There's no difference between a maj7#11 and a maj9#11. Technically, you could say that because the ninth is not specified in the one, that it's not meant to be there; but in practice, any flavor of 7th chord is equivalent to the same flavor of 9th chord. Maybe in pop you'd be that specific, but in jazz (the most likely place to see that chord) you'd nearly always substitute the 9th for the root, thus spelling a Cmaj7#11 as E G B D F#. That's especially true if the chord includes an 11th or 13th, which implies that the 9th is also present. Still, you see it notated that way, and I think it's an odd omission. If only one were available, I would think it would be the maj7#11, with chord embellishments providing the 9th.

+1