My only experience is with the Monster systems, both the captive system and the articulated arm system. Both have been workhorses, although I prefer the articulated arm. I've comfortably hollowed 4" to 6" deep hollow forms, and I've hollowed as deep as 11 1/2" on a vase using the 3/4" boring bar, although at that depth I was pushing the limits of the tool and/or my skills. With a 1" boring bar I'd expect to go that deep and a bit more.
The Kobra system is a beast...the Lamborghini of the market. (And I'd put the Monster tools at the Lexus level.)
Disclaimer: I run the Monster Lathe Tools website for my friends Todd and Michelle (who make the Monster tools), so I'm probably a bit biased.