For years, the Canon version was regarded as the best amongst the cheap lenses out there. Sometimes it was under $100 though most recently it’s around the $120 mark. The Yongnuo version is far under that at around $40.
In their test, Kai finds that the Yongnuo 50mm f1.8 is pretty darned good–though the focusing motor is probably one of the most annoying parts. They found the Canon 50mm f1.8 II to be faster to focus by a hair and they also found the Yongnuo to be worse than Canon’s. Oddly enough, others (like Tony Northrup) found them to be comparable.
The rest of the video as well as the results of their test are after the jump.