Keyboard Tray suggestions (under desk mounted)

[metropole]

I convinced myself that I want to try out an under desk mounted keyboard tray.
Just wondering if anyone here is using one and researched the different models.

One main difference appears to whether the keyboard and mouse pad rest on the same surface or the mouse is a separate (attached) pad. Wondering if anyone can offer pros and cons of the two approaches.

Here is a model with mouse separate:
https://www.amazon.com/Mount-Keyboa...e=UTF8&qid=1541165017&sr=1-2&keywords=MI-7135

This one together:
https://www.thehumansolution.com/knoll-adjustable-keyboard-supports/

And then there is the question of what brand to buy.
Mount-It appears to be one: https://mount-it.com/collections/keyboard-trays-mounts
The Human Solution appears to be more a store for different brands: https://www.thehumansolution.com/ke...w-to-choose-the-best-ergonomic-keyboard-tray/

Any thoughts are welcome.