There's reasons to play both tbh (or rather, all 3. Even though it too is run by Sony, EQMac is basically a different game than Live AND P99). There's also no real reason you can't play all of them at once.
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Ultimately. Play the ones you think you'll like most, or play them all and remove the ones you find you dislike. And I agree, asking this community is a terrible idea. Most will pick P99 without an eyelash bat and will spew anti-modern propaganda. Just like asking the Live boards will always pick Sony's servers and spew anti-Classic/Emu propaganda. You'd be better off asking a completely neutral source...or better yet, just playing what you want (as previously stated).