As a bit of Prusa fan boi myself, I too would recommend the Core One over the Mk4s at this moment. It’s a matter of “Buy once. Cry once.” Cheap often costs more in the long run.

When you are facing a 30 hour print or a long project, a bit extra speed is not only nice but helpful. Plus the heated enclosure can provide access to more engineering grade filaments. While you might not need to print nylon or ABS every day, you will probably find you are going to want to at some point a bit of those types for a project or two. And I believe the Core One also has filtered exhaust air to control nasty fumes that FDM printing can cause, (yes, even PLA has particulates that won’t kill you immediately, but they ain’t good for you either long term).

Personally, I find the MMU to be a god awful design mess. A rat’s nest of loose tubes and spools of filaments, but it does work. I might consider the Box Turtle over the MMU just for the neatness of the design. I find the multi-filament units, cool for very little color printing I do, but it’s the ability to use up spools that don’t have enough left one them to complete a print by switching to a different spool that can finish the print automatically to be far more valuable. It’s cut down my clutter of mostly used spools to near zero. I paid for all that kilo, I’m bloody gonna use it all dammit.