The problem in my case may be that after I collect a bunch of TV series recordings (like a weeks worth), I go back and do a "group update" using "get Movie & TV info", which then is allowed to overwrite the description. I have not noticed if this update process actually changes the description or not, but I know it adds additional information (like aired date) that is not coming from my EPG data source.
When I was using the "OTA" EPG data (a few months ago), I did not get the season and episode numbers so in that case looking at the show's description made sense. However, now that I use xmltv (Zap2it) for my EPG data, I get consistent series, season, and episode data.
Perhaps MC could offer a choice where the User could select (via check boxes) what fields (like Series Name, Season Number, Episode Number, Episode name, date aired, and/or Episode Description) to have MC compare to determine if a show is already recorded, I think that level of customization would fit everyone's situation.