Glad to see this getting traction. Marlin was getting long in the tooth, and Klipper is a nice upgrade for every non-Prusa printer I've got. We're even starting to see it supplied by the manufacturer in some cases, e.g. the FLSUN V400.
What is wrong with Merlin? It's older but that could mean they have more features and ironed out more bugs.
The math used in each system to control the rate of flow is very different, I believe Klipper's approach gives a much nicer finish. On top of that, Klipper can also compensate for the resonant frequency of the physical frame+substrate of the printer to minimize artifacts and patterns in the final print. You can tune Klipper as much or as little as you want.