Have I got some data for you....
http://type4power.dyndns.org/video.htm
I have some videos comparing mufflers on a 2270. I was running a Super Turbo muff (pretty much like the Dynomax you are talking about) and then I switched to a 40 series Flowmaster.
The flowmaster does flow better, you can actually feel a difference.
But, it is... Ahem, a bit more aggresive. I like it.
Later,
Tom