I’ve not seen the Z-plus in the metal so can’t really comment on that unit, it seems well designed though, linear rails instead of V Wheels etc.
As for the spindle, the only upside to the 80mm spindles is the larger ER20 collet going up to 13mm tool shanks. This lets you use a whole range of edge finders, probing tools, bigger cutters etc. many of which are quite a bit cheaper because they’re made in volume, 1/2" cutters for carpentry for example. It would take a lot to pry my ER20 collet out of my hands now…
You’re right, I’ve never used more than a few hundred Watts of my 2.2kW and if I could have bought an 800W or 1.5kW with an ER20 collet I’d have done that, but I couldn’t find one and we have 230V AC standard in Europe in every outlet so no special wiring for me 