Multi extruders are a real pain to setup and adjust, and this has to be done any time you change the nozzles.
The Prusa XL has load-cells in the extruders. You just take off the build-plate, put the calibration pin in the hole for that purpose and select "calibrate extruders" (or similar) and it taps each extruder in turn against the pin from 4 sides a few times (just like a probing macro with LinuxCNC).
Admittedly it's not the cheapest of printers, but I don't regret buying it.
