Do they compare?
Absolutely.
I have Marmot bags, Kelty bags, Western Mountaineering bags along with the Camp saver bag, in my backpacking arsenal.
I put the camp saver bag in the same category as the marmot and kelty bags.
I had the same thought that you had. Its a lot of bag for the price. So, I bought one. With the sale that they are running now, -$100 off regular price, it cant be beat.
I wish they made a -20 bag. The 850 down - 20 bags are spendy. If campsaver had one, I would buy it rather than spend the money on another western mountaineering.
Western Mountaineering bags are the best if you ask me, but they make you pay for it.
I would love to see a campsaver option.
I also wish they had a waterproof version. The 10 degree bag I have says it is DWR treated, and I got it wet during a rain/hail/snow storm last august. It was bad weather for 3 days and it was always in the back of my mind. Peace of mind from a waterproof bag is worth a little extra in my mind. The little bit of wet didn't hurt it, so I guess the DWR did its job.