Hi flow catted H pipe/ shock H

[gcstang]

I want to replace my stock H Pipe with a high flo catted H pipe. But there seem to be more O/R H's and more catted X's than there are H Pipes. I heard the reason is the stock H flo's just as well. There are more X's because they flo better and give you a better top end.
Is there any truth in any of that ?