Fostex T500AmkII

I heard a pair recently...
I liked them, as did everyone else present (including some very experienced ears).
Nice tone, clear, adds "shimmer," and different timber to different cymbals, brings out triangles, etc, without "sticking out," and calling attention to themselves.

I heard them in a "3.5 way" horn system,
above a LeCleach/Lowther, sitting on a Khorn, w/ a sub.

If they weren't so pricey, I'd consider using them in either the 4 or 5 way horn systems I'm building.
 
I haven't heard ALEs, but to my ears the T500AmkII sounded as nice as I remember Goto supertweeters. Much better (clearer, less harsh) than Fanes too.
And quite a bit less $...

I haven't heard a ribbon that I thought was in the same class, but did try with AMTs, and LCYs for a while. They always "sound like a ribbon," have their own sonic signature which really sticks out, and sounds "different" from the rest of the system to me. A "tinny" kind of sound that's on top of eveything else.
But many people like them, YMMV, etc...