I’ve had several maple neck PRSes, including one of my current 594s, a McCarty, and two CU22 Soapbars, and a couple with mahogany/ebony. I’ve also had a few rosewood neck PRSes, but with rosewood fretboards.
It’s not that the maple/rosewood is brighter; with a more scooped midrange, the treble seems a little snappier and brighter because the tonal balance is different. You get slightly more of a “flute” sound, for want of a better description, in the neck pickup. I don’t hear a huge difference in the bridge pickup.
The biggest difference with ebony is that the note attack is very fast. Again, that gives the impression of brightness when actually it’s more of an ADSR envelope thing.
I think you’ll find that mahogany/ebony is going to have more sparkle than rosewood/ebony. Rosewood necks seem to accentuate the lower mids a bit, however, the combination with ebony seems like it’d be interesting.
