When wide content exists during a compare, horizontal scrolling (inline or browser) never appears for us.
It's the classic problem with IE, most likely CSS related. We can get the inline scrolling to work but we couldn't figure out how to balance columns or recover the browser's horizontal scroll in our limited timeframe.
For our situation, we found a workaround by adding CSS to force images to a certain width (copying the code snippet display). But it would have been nice to have the inline or browser scrolling to work consistently OOTB between the two big browsers.