I have the ball mount, with a stiffener below that dash. It's rock solid. I did use it without the stiffener first, and while I noticed a little bit of bounce under some conditions, it wasn't enough to really worry me. And that's with a really heavy old 2730 GPS. With a more modern, lighter unit, it would be even less of an issue. I added the stiffener more as a matter of curiosity than any real concern about the mount.
Edit: I just went an looked at the articulated one. I thought you were asking about vibration from the dash, not the ball. The only time I've noticed an issue with the ball was when I first installed it with a plastic RAM mount. The weight of the GPS caused the plastic to fatigue, which resulted in a lot of vibration. When I replaced it with a metal RAM mount, problem solved.
What I like about the ball mount version is that I can mount things off center if I want. I have the GPS mounted to the left, which leaves room for an Aquabox on the right.