The Logitech G840 is like the G640, only bigger. You're more likely to find comparisons if you search for them.

The Logitech pad is a lot faster than the QCK, especially when new, in terms of both static and dynamic friction. The QCK feels like a "mudpad" compared to a new G640/G840, good for games like CSGO/Valorant but tracking heavy games like Apex or Overwatch are a bit harder. However, since the Logitech has a coating, the pad becomes a lot slower and inconsistent after a while, especially after washing. Generally advise against coated pads unless you want to get a new one every few months or don't play shooters so you don't care about the inconsistent glide.

Unfortunately, I can't offer you a comparison. However, I would recommend a mouse pad with sewn edges. Glorious PC Gaming Race comes to mind with a good example.