My subs are designed to have the driver face the wall. The reason is, I hate making grills, and that way I can get away with not making them. Since I don't have amps or anything else on the "back" of my subs (their amp goes on the equipment stand), I can get away with it.
When the woofer cone is within an inch or two of a room boundary, there is a modest increase in effective moving mass from improved coupling with the air, slightly raising the Qts and slightly lowing the Fs, which together will boost the very low end a little bit relative to the rest of the spectrum. We get that benefit without the effects of cone sag that a downfiring woofer would be subject to (yes I know cone sag is theoretically of negligible significance in most cases, but I'm not sure whether that would still hold true after many years of use as the suspension system softens up).
I don't see an obvious advantage to woofer-facing-the-wall as far as room interaction goes, nor do I see an obvious disadvantage either.