Going from the Sony brochures on the vinylengine site, the PS-X45 and PS-T33 were offered at the same time as the PS-X75 when the biotracer arm was introduced, so the statement that they were offered after the biotracer was abandoned is not accurate.
The X45 has slightly better rumble spec., quartz lock, electromagnetic braking, lower-capacitance interconnects, heavier platter, height-adjustable fluid-filled feet and overall heavier (about a lb). Both appear to use the same arm and 'Sony Bulk Molding Compound' in the base (so the T33 is not 'plastic') and BSL motor.
To answer your original question, the X45 is the better turntable and it looks like the T33 would be a pretty close match for parts (but again the speed control circuit, etc. would be very different).
I don't agree really that these were offered in Sony's decline period - they were smack in the heydey for big Sony turntables with the PUA-7 / Biotracer / X-TAL lock technology ... although the X45 / T33 offered lower mass straight tonearms.