I would love to purchase two more Ergotron LX's. I have one at the office and it's a solid piece I can just take for granted will be there for me. Holds a Monoprice 27" Zero-G 2560x1440 IPS, usually extended 2' from the pedestal, without complaint.
I frequently re-position throughout the day, and nothing has gotten weak in two years of use. Even if it did, tension can be re-adjusted.
Having used the LX, I'm not interested in the Vivo arm. I've not seen the Vivo in person, but it resembles the Ergotron 45-174-300 Neo-Flex LCD Arm, which I found generally unsatisfying since it does not have the range of the LX.