2013 was the start for my first 3D printer, only with some experience with a DIY build CNC mill (2009), with the desire as far as possible a homebrew printer, to learn from.
The choice was Mendel90 sturdy

However, right from the start with some small changes for more mechanical resolution as eg 42BYGHM809 0.9 ° stepper motors for XYZ

The X-axis pretty soon replaced for the improved version, another X-carriage for 3mm mounting plates with various extruder’s on it, for quicker switch between 3 and 1,75mm filament

Regular switching between different extruder’s, means also re-adjustment Z-endstop and steps/mm by filament diameter and a proximity sensor on the same 3mm mounting plate or integral to extruder-body only when changing the nozzle.
But the space is limited between the bars by horizontal orientation and there are also some cooling needs (PLA, ABS, PETG)

Vertical orientation as the Prusa i3 offers more options to quick change the complete head from mono direct feed to Bowden multi feed, without many other setting changes for an simple network 3D printer
A multi-filament one nozzle hotend as 3in-1out is a great three colour nozzle with possible a rainbow on colours, but without active mixing, helps that not with “stripped toothpaste” effect.

By changing the X-axis there are a lot of options/choices with DIY.
Quicker printing, another way auto-zero Z, timing belt transmission with custom big-gears for same steps/mm filament, and so on