i have the avid 8wt 9'6" n love it, great pole to fish anything with.
seems to me the difference is how stiff the rod is, i'll agree with st croix, its a moderate action rod(avid). so i think the big money difference is the big demand for ultra fast action rods. every company that sells a light fast rod has it at a pretty penny.
and to even further my point, i had to warrenty my tip section, clipped it with a clouser. and the replacement they sent me is slower than the original one.
i think the question would be do you want a fast action rod or a moderate action rod? that would answer your question. or better yet go cast the both of them(if you can), and see which you like better.
tough that single haul kelly does in that vid, on the st croix site, is soooo sexy!
good luck man