While there are many mfg. for square ballast, There might only be one real mfg. on the round 50W (50W/38W) ballast in China, so all these brands are most likely selling the same ballast based lights.
Some vendor may have better reputation, do better service or do better marketing job on Forums, but the components are unlikely to be different. The ballast (With integrated lamp) looks identical in all case I've seen. They all have 3 contact rings on bottom, one for neg. & two for 38 or 50W hook up. If the light is 50W only, it'll skip the 38W hook-up but it's still there.
I found the ballast on Ali express, ordered one for testing.