X & H pipe vs straight dual exhaust

I had independent 2-1/2 pipes on my gold Barracuda when I put the 360 in it. I just hooked them up to my Spitfires. The exhaust note seemed a little sharp to me so I added an H-pipe. Torque went noticeably up and exhaust noise went noticeably down. Top end didn't seem to change. About a year after I did that a friend gave me a new 2-1/2 exhaust with Borla mufflers he pulled from his Mustang. I swapped just the mufflers to begin with and the exhaust note was mellowed but louder with no other noticeable change. One day I cut up what was left of the Mustang exhaust and welded it, along with the X, to fit the Barracuda. The difference that made was a quieter and more mellow sound and new pipe. My observation would be that the H or X pipe are almost equal improvements over the independent pipes in that they add torque and soften the exhaust noise. I don't think that is anything new, just a personal confirmation.