If [still a big "if"] the Democrats take control of the House, the biggest difference would be that most if not all of the Repub obstructionism would fall away.  The biggest benefit for the public would be that we wouldn't have to endure any more congressional witch-hunts like the "Benghazi committee."

Actually, if the Repubs were to loose control of the Congress it would be a good time for a strategic retreat from their failed policies to obstruct all the progress that voters are calling for.  The Repubs could retreat into grouchy opposition that wouldn't mean anything while they figure out if they still want to be a political party after being assaulted by Trump.