You are not quite right if I understand the way you are thinking about it. The steel ball bearing in the Manix wedges between the steel blade tang and a steel liner. The polymer cage part you have read about is simply the polymer piece you can see on the outside of the ball to aid in purchase on the ball bearing. I seem to remember one case where the cage (which is two pieces with the ball sandwiched in between) came apart. I would not worry about it at all. There are non-caged ball bearing locks. I like both designs, the cage is functionally good, but the open ball is a lot neater to me. I think the only "knife" that has an open ball available right now is the marlin spike on the Tusk. The Phoenix, Dodo (that may still be available), and some others have used that design. The steel or ceramic ball can be slippery so the Manix employs the caged version.
Have no reservations with either knife. I would personally have reservations with cutting copper wire myself, but I have played around with my Manix in S110V with hard wood, and the steel did great. I would not recommend either folder for long term whittling though. You need a good contoured handle for that, and most likely only a fixed blade will give you that, not to mention a Scandi grind would excel at wood. And yes, you should get a Gayle Bradley eventually, if not now.
I'm glad you clarified the ball-bearing lock for me, I'd feel a lot more comfortable buying a knife like that. As for the copper wire, it's certainly not something I would WANT to do, but when wiring a house, untangling something, etc sometimes the only wire-cutter within reach is your pocket knife, so to have something that wouldn't be completely wrecked by such abuse would certainly be a plus.
As for the whittling, I suck at it and don't do it often, that was just the example that came to mind.
