The smaller one.
Well, yes and no for the double-base system (diecast AL + SBMC + wood) was shared with the TTS-8000 monster - very efficient and quite good-looking, too. SBMC is btw mainly made of polyester and fiberglass.
The carbon of the armpipe, antistatic lid (less darkly tinted), gel-filled feet, fluid-filled mat and diecast aluminium top were imported directly from the PS-8750 elder.
The motor is the new BSL with two Hall elements which Sony would use in various guises for all its subsequent 'tables : PS-X70, PS-X700, PS-X800 and variants.
However, 1 : the tonearm of the PS-6750 is not a PUA-1600S.
However, 2 : the dustcover has a different shape and is clearer in tint and much thinner.
However, 3 : no X'Tal lock and the IC in charge of speed regulation isn't the same.
Yet, smaller, yes, ok, but frightfully reliable and very very good looking, too.