The biggest single advantage for vapor return from my seat is NO VAPORLOCK. First car I ever saw with a factory return was my '70 sixpack RR--my '69 383 didn't have it.

I wasn't sure how well it worked, until I'd put an "electronic" pump on in the early '70's. I didn't know these pumps didn't shut off, so I defeated the vapor return so "the pump would shut off." Not only did the pump NOT shut off, but if I didn't run the thing, the car would almost guaranteed vapor lock with only the engine mounted pump!!