There is a structural difference between the Ironridge XRS and XRL rails. The XRS rails are heavy duty rails and they are used for longer span requirements.
For sites with high snow load and strong wind conditions, I'd recommend using the XRS rails. Otherwise XRL rails are as sturdy as the other rails manufactured by other brands.
I am now comparing the certification letters of XRS (pdf) and XRL (pdf) rails.
It seems that, at a Category B zone, wind with 90 mph, and no snow load,
the XRS would allow 11' 6" max. span, whereas
the XRL would allow 6' 6" max. span.
Comments
There is a structural difference between the Ironridge XRS and XRL rails. The XRS rails are heavy duty rails and they are used for longer span requirements.
For sites with high snow load and strong wind conditions, I'd recommend using the XRS rails. Otherwise XRL rails are as sturdy as the other rails manufactured by other brands.
I am now comparing the certification letters of XRS (pdf) and XRL (pdf) rails.
It seems that, at a Category B zone, wind with 90 mph, and no snow load,
the XRS would allow 11' 6" max. span, whereas
the XRL would allow 6' 6" max. span.