The problem with the A scale is that you'll need a 29 frets guitar for some parts in the intro , but with the E scale you only need 24 frets which is quite popular.

If it's transposed for guitar in A scale , you'll have to cut some pieces of the intro's run which narrows it's sound.

In Becker's vid , it's around 150-160 I think , and if I remember right it was in the A scale like Vai's... He didn't play the intro , and there was some improvised stuff.