According to Knight the 209's are hotter and more reliable. With pellets that is what they recommend using with their disk rifles, although #11 caps will work. If you want to use #11's they recommend using powder. But not vice versa, i.e.,if you want to use powder in order to customize your load, they still recommend using the 209's.

So it seems from their testing the 209's have the advanage at least with the disc rifles.