IMO Remington is the superior gun... Not even a close comparison.
However, I own the Mossberg. I got it when the 2 shotguns were newer on the market and the price difference was the factor for me at the time. My 835 shoots fine. I have none of the problems you mentioned. The action is stiff and "sloppy", however, which means you have to work the action pretty hard to eject a 3.5" shell. But, that's not really jamming... just a lack of elbow grease on some folks' part. <img src=icon_smile_wink.gif border=0 align=middle>
Either gun will "get you there". But, the Rem is a more refined firearm.