Subwoofers down-firing or side-firing? Why?

I own 2 RELs from a similar era, a Q108MKII down firing 8", and a Q150e front firing 10". They are GREAT subs and work swimmingly together. Bought used at different times for about 200 bucks each...make my own cables out of Canare quad.

According to Louis at Omega, he uses down-firing subs for ease of placement.

I've tried both configurations with the exact same subwoofer.  With downfire, you do hear the bass, but you don't get nearly as much "punch you in the chest" type of sonic impact.

The Sub-x sub from Golden Ear has too side firing active drivers and a top and bottom firing passive radiator. Its much easier to get the placement right.

"....Downfiring subs allow the bass wave to move in several directions in the room at once. The problem you have with bass in a room is standing waves which can cause cancellation at some places in the room and re-enforcement in other places. By having the bass radiate in several directions at once, its easier to place the sub or subs so you can get more uniform bass because some of the standing waves can be less pronounced...."

I believe that is Rel's position on the matter, making for easier integration.