From the video it looks to me like the x pipe equalizes pressure in the pipes at high flow and the H pipe does this at low flow. With my xpipe in my 5.0 I at WOT I was past the redline for rpm when the AOD would shift. That and the drone/loudness caused me to use the dual in/out resonator instead and I added high flow cats. I don't know v6 motors so about all I can say is the xpipe was louder with no cats.
I read the 4.6 handles over 1000 more rpm and it might not be past the redline before shifting. The 4.6 guys generally have the ability to control shifts electronically too.
1992 Tbird LX 5.0, 3.73 gears, 1995 Cobra intake, deleted air silencer, 2.5" mandrel bent dual exhaust, SCP shorty headers. Updated four-hole fuel injectors. SK shift kit in AOD. Vogtland 0.9" springs, Tokico and Bilstein shocks.