The Newtown-Slocom is one of the best vinyl replacement windows....way better than the 5050 from Simonton. Simply look at the U-factor and SHGC.
If that's what you think makes a good window, I shudder to think what other nonsense you tell your customers. I would put Newton-Slocom on an equal par with the Simonton 5050. I would put it way below the better Simonton Windows and far below the better windows by Sunrise, Okna, Gorell and Soft-lite.