Here are the things I love about Mint:

• Everything is doable with a nice GUI, sometimes more than CachyOS+KDE Plasma
• Very stable, very reliable
• Mint's Update Manager is great
• Matches my personality/philosophy a bit more
• I installed it for my mom after her old drive died, and it just works for her (she is not a computer person so this is a big win)
• I quite like Cinnamon, though my feelings on this aren't that strong, I'd be happy with just about any sane desktop environment

Here are the reasons I switched to CachyOS:

• My hardware is new enough that it really benefits from being up to date on everything upstream. On Mint, it's not hard to switch to a newer kernel and stuff like that, but the more I stray from Mint's defaults, the more I have to do to maintain my PC rather than just using Update Manager.
• I could not get VRR (FreeSync) to work on Mint Cinnamon. I think it might be impossible.
• I wanted to try other desktops like KDE, and see if Wayland makes any difference to me as a user (it doesn't). Mint's supported desktop choices are quite limited (just Cinnamon, Xfce and MATE) and I didn't want to screw around getting an unsupported desktop to work, defeating a lot of Mint's advantages.
• Generally wanted to be on the bleeding edge of software updates, just because.

I do have some qualms about CachyOS, specifically I feel like Shelly (their choice of GUI package manager) is undercooked and not ready to ship as default. You don't have to use it though.

I'm going to stick with CachyOS for now, mostly because it's just working for me and I don't feel a strong reason to switch. I hear that Mint/Cinnamon is getting closer to Wayland, which might make for a good time to switch back to it. Or I'll just stick with what's working for me until it doesn't.