I am a satisfied JPS Speedster owner. Before buying, I thoroughly checked out the major replica builders - paying personal visits to Vintage and JPS (didn't make the Canada trip - IM was way too expensive).
When I decided to get a Speedster, I wanted it to be as authentic as possible, but I was also concerned about quality. I found that both Vintage and JPS made very nice cars and their prices were literally within $100 of each other for similarly-equipped cars.
I opted for John Steele at JPS because his cars were built one-at-a-time and his idea of quality construction was similar to my own. (This is not a condemnation of Kirk at Vintage). I felt that JPS was a specialist, while Vintage was more of a "generalist."
When I see a post saying, "a JPS is essentially a Vintage Speedster rolling kit that John then finishes," I just cringe. JPS and Vintage do, indeed, get their "parts" from the same sources, but it's how they put them together that makes the difference. The two manufacturers make similar cars that are "essentially" quite different.