The experience I have on MK4 and X1C are similar, as far as reliability, etc.

There's different annoyances for each; if you calibrate each time X1C is slower to get going. X1C is faster overall on bigger jobs. X1C has weird wifi error-out issues more often. MK4 gets a bit more gunk on the nozzle. X1C wastes more filament. X1C had some issues with retracting filament at first that I printed someone else's bracket design to fix, while MK4 just worked. X1C quality seems slightly better with PLA; MK4 does a slightly better job with PETG.

When wear makes major maintenance necessary, it's going to be easier on MK4.