Why didn't Sheldon want to live with Amy, but did with Leonard?

In one older episode, I believe it was season six, Sheldon is looking for a roomate to replace Leonard and Amy offers herself as a roomate. She gives him very good reasons why to live with her, she is MUCH better and assidious roomate than Leonard and Sheldon can't refute any of that. So why did he desperetely DID NOT want to live with her? What was the REAL reason?