Subwoofers - Front Firing or Down Firing - Which Sounds Best?

Any advantage to woofer cone facing toward listener as opposed to firing down to the floor? Thinking of upgrading my 20 year old B&W ASW-650 sub to get that oh-so-pleasing belly message which lives in the 20-ish Hz range (very rare I know). SVS has the "tube" subwoofer (PC-2000) at a reasonable price. Just wondering if the floor-firing model would disappoint? Wouldn't want the hassle of returning if it did. Any opinions? Current users? Thanks.