I've been playing acoustic guitar for 33 years, semi-professionally for most of that time, and consider myself a pretty accomplished player. Never put brass pins in any of my guitars, nor felt a need to. Ebony works well, and generally looks better (in my opinion). I've played guitars with brass pins, some of which sounded good, some of which did not. Some components of a guitar will definitely enhance or impair the sound, but in general I am skeptical of people's claims about different bridge pin materials; if the pins fit well, they should do the trick, whatever they're made of. You may hear subtle differences after changing the pins -- perhaps for the better, perhaps not -- but you're just as likely to hear the same magnitude of difference when swapping one set of ebony pegs for another.

I'd say put in (or leave in) the ebony pins. If you have a good guitar, good quality hardware (tuners, nut, frets, bridge saddle, etc.) that fits well, good setup, fresh strings, and you still feel a need for sonic improvements, work on your technique.