If they were face to face,Lelouch could just order Light to die or Lelouch could use the Black Knights to help him. As long as Light doesn't know Lelouch's face or name then it's fine. But Lelouch wears the Zero mask.

Yes, Lelouch would be more likely to defeat Light. Besides, when there was something that Light REALLY wanted to accomplish, he barely did it on his own. He manipulated and used others to get the task done, which Lelouch is also guilty of, but I think that Lelouch is more likely to succeed on his own.