I am not a big fan of Bradley, but he only lost twice in his entire career, and was never knocked out. And, he fought plenty of fighters who hit as hard (if not harder) than Gatti. Conversely, Gatti was stopped by a number of fighters smaller and less skilled than Bradley. If anyone is getting stopped, it is Arturo.
I like Gatti, but he was at his best at Super featherweight, and 95-98 Patterson-Robinson time frame. He had some fun fights and good performances but nothing great. If he struggled with Robinson at 135 he is in for a world of trouble from Bradley at 140. Not sure if Gatti gets stopped outside of cuts in this fight, but he loses very convincingly. I like Gatti and am not big on Bradley but Bradley wins this wide and convincingly.