Ron:
I agree with you that downward versus front firing should never be the primary criteria when selecting a subwoofer, but surely there are specialized situations where one design might offer some advantages (assuming we are considering comparable, high quality products).
Getting back to...
There are of course special situations where a front-firing subwoofer would have advantages over a downward firing subwoofer.
For example, when it is necessary to place a subwoofer in a cabinet a front-firing subwoofer is better. Sunfire builds their Architectural subwoofer series specifically...