The thing with Own3d was that for the most part its streaming service simply did not match that of Twitch. The layout and mobile support was a bit better (streams that used Own3d were far more convenient to access since they played from the browser), but the quality was lacking. Twitch, on the other hand, has focused on what matters: the stream quality. Now that there layout has been updated, they would have smoked own3d even more IMO.
Many streamers moved from Own3D to Twitch because Own3D was not making good on owed payments. Twitch needs competition to force it to improve its ToS, but it's been good for gaming.
