It has also been my impression that downfiring/frontfiring is aesthetic.
These subs we're looking at are all EQ'd flat - so what difference could front/down possibly make?
From a placement standpoint - your downfiring sub is ALWAYS a certain distance from a room boundary. A frontfiring sub - not necessarily. So it would make sense (to me at least) that a front firing sub would offer MORE flexibility w/ respect to room interactions than a downfiring sub - which is always x" from the ground...
The aesthetics and kid/pet-proofing makes the most sense to me.
FWIW, I have a front-firing sub placed at the back of the room and most people that have experienced movies at my house think it is furniture until I take off the grill. The MBM-12 I have is placed more toward the front of the room - and it's downfiring.
During placement, the same spots were good for downfiring in the room vs. frontfiring. Makes sense, since the room shape didn't change between my moving the different subs around the place...
I can say with absolute certainty (based on both theory and experimentation) that placement is going to make a massively-huge difference in performance. I don't think anyone can say with confidence that the same is true for down vs. front.