I'd imagine that if not exactly, they likely were very close to same quality, since they essentially were custom-/hand-made one-offs produced in extremely limited quantities to ultra wealthy buyers accustomed to very best and finest appointments and detail any high-end coach-built motor vehicle manufacturers could offer. One should compare these with a modern "special order, SP-, etc models rather than "standard"(?) V8 or V12 production cars. The "pumping out road cars" didn't really start until later (late '50s/early '60s ?) when demand grew enough for the company to afford manufacturing of more modestly(?) priced, larger scale production cars.