I have spoken to Garth at Musical Surroundings about the Ebony LP vs. the Ebony LP-S. And I have carefully compared the specs and physical appearance. The ONLY difference is the use of brass for the structural frame, vs. aluminum. And the only significance to that is the cartridge's mass. There is some hype that brass's greater mass may provide more damping. But the really IMPORTANT thing for any potential buyer to think about is his arm's recommended cartridge mass to keep resonance within the right frequency range. The arm's effective mass, the cartridge's compliance, and the added mass of each cartridge will determine his cartridge/arm system's resonance frequency.
With the vast majority of tonearms designed for a moving coil cartridge, the new LP-S is too heavy. So, with an LP-S the resonance frequency will go up into the audible frequency range, above 20 Hz. And this will definitely have an audible effect upon sound.