Certainly both that you mentioned, although there are lines of each that get pretty hairy. Maybe consider the 3...b6 lines against the French Advance, and the Fort Knox against the mainlines.
The Caro-Kann probably qualifies.
But if I were going to pick just one really slow and solid setup against e4, it would probalby be the Philidor with Be7...Re8...Bf8 type lines.
What can be played as black against e4 that would be considered a very quiet/positional defense? Modern? French? Any others?
-Ted