4T 50 cc scooters are not very popular where I live because they are MUCH slower than 2T 50 cc scooters.
As I said, 50 cc scooters are usually driven (at least here) by kids who do not have the license for a car and they are all going for performance.
The most popular scooters are Piaggio NRG 50, Aprilia SR50 and Gilera Runner 50 because they offer the best performance (the fastest are the models from 1999-2004).
I had Kymco Cobra 50 2T and it was extremely slow compared to my Piaggio NRG 50. I do not know if Kymco has meanwhile improved 2T engines in its scooters.