I'd say our typical tree run is around 300M long, but I know of a few areas that are longer. Heck, a run down Powder Fields (inbounds at Red Mountain) is somewhere around 700M of trees that are so well spaced, they don't really dictate your turns, combine that with 3 or 4 small/medium cliff bands you come to while skiing the run, it makes for a killer warm up run on a inbounds pow day.
As I said earlier, when talking about the West Kootenays, you can't think of it as who has the best tree RUN, If you are willing to tour, we have more tree skiing than you can shake a ski pole at, and it's all amazing.
Mostly a cedar/hemlock forest with spruce, fir, and pine mixed in at different elevations. When you get into a grove of big guys with a full canopy and clean understory, getting blower face shots every turn on your way to a 4 stage pillow line.
Didn't want to bring up the cat/heli skiing, but there's a reason you know of the amazing tree skiing that exists at the cat/heli operations that practically all sit within the boundaries of the Kootenays.