I owned a ULA P-2, which was the predecessor of the Catalyst and similar in design, and have tried several GoLite packs (though not the Quest). Regardless of the published load ratings, 40 lbs is more than I would recommend for either pack.
Most ULA owners report that they love their packs; I am probably a minority of one. My main complaint with the P2 — and it was a deal breaker for me — was the design of the shoulder straps, what ULA used to advertise as the "cradle suspension." The straps connect to the bottom of the pack rather than the conventional attachment point at the inside corner near the waist belt. The effect for me was two-fold: it tended to pull the straps back into a sensitive area of my armpits and transferred a greater fraction of the load to the shoulders than I wanted. You cannot fully unload the shoulders and transfer as much weight to the hips. At 25 lbs it was a very nice pack. At 40 lbs I found it very uncomfortable. A second criticism of the new designs is that they no longer offer a top pocket, an option which I happen to like. Other than these two complaints, I think the packs are very good.
I like some of the GoLite products, but based on my experiences with older GoLite packs, I think there are probably better choices in that load range. I wouldn't choose one for heavier loads and longer trips.
Some people report that both the ULA and GoLite torso lengths are overstated and find that a size larger than they normally use is more comfortable.
I switched to a McHale last year. If you've got the money, in my opinion there's simply no comparison; I wouldn't even consider the other two for that load range. For less money, I'd consider the Osprey Aether 60. I have found it very comfortable at 35-40 lbs.
Let me emphasize that I think both ULA and GoLite are great companies with innovative products. Just didn't work for me.