It kind of depends on what kind of setup you want to have. Desk mount vs Wall mount, movable arms vs fixed angle, these are thing's you'll need to decide on.
Ergotron is generally one of the best manufactures out there, but they're also one of the more expensive ones. I use the LX Dual Stacking Arm, which runs about $250 on Amazon. I use dual 24in IPS panels are are a bit weighty and they work beautifully for this. Amazon makes what are basically Ergotron based arms, but I don't know what their quality is like but they are much cheaper.
I highly, highly recommend arms for a dual monitor setup, it nothing else being able to control the height of the monitor does wonders for the neck and back. While desk mounts can take up some room behind the monitor they still make up for it with the desk space they free up from using stands. However if you can get away with it, a wall mount would make things much easier but it means you have to have a stud in the right placement of your desk. I would not trust a simple drywall mount with the 20+ pounds hanging off a small mount point.