Man, if you look at Orton's sack numbers throughout his career, they are not that high.
If you really want to compare EJ Manuel with Orton, Manuel has actually been sacked at a greater rate than Orton has throughout his career.
And Orton hasn't really been playing behind the same line as EJ.
If you want to know why the line seems worse with Orton in there, look no further than this guy...or at least start here:
http://i.imgur.com/Wiy1GxH.gif
Cyril Richardson has started every game Orton has, and he's been absolutely putrid. He's only started one game with EJ at QB...you know, the game which was the last straw leading EJ to the bench. J.J. Watt basically won the Bills/Texans game for Houston, IMO. You know something is wrong when fans are screaming for Urbik to start...