With those flat plates I’m printing, there’s zero difference. But when I have to print tall thin things, like for example a long tube to adapt diameters, it’s doable without any support on the XL, while I need a gigantic raft and glue on the Mk4 - and even then, it shakes enough that the diameter is not that great at the top.

Also, the XL has two heads, so I can print TPU with PLA support.