I bought a set of long off-road slash cuts when I first got my 03 TA. At that time there were 3 different versions of them - Triumph was trying to find the right sound, I assume. The mechanic at my dealer put them on for me and made the statement that you could look right through them, so the prior versions must have had offset baffles in them.
I put a few thousand miles on them and thought I liked the sound, but after awhile they got real raspy and annoying. I took the plunge and bought Thunderbike pipes and have lived happily ever after. A decent low tone and a performance increase you can feel. But they're not cheap...
I don't know what the Triumph off-roads of today sound like, but I bet they still don't match the TBike pipes.