TL;DR - With small-ish metal income, caretaker flexibility is better. With great metal income, plates become better.
Katastrophe - That was mentioned with the walkoff scenario. And yes, the indirect buff to spiders is... nice. I find myself less annoyed with spiders when i get about 30m/s. My usual all-rounder queue is 15 fleas, staggered 4venom 2 redback 3 recluse 2 hermit. With about 40BP and 30M/s, the 15 fleas tend to be the point where i stack up a lot of metal. Sometimes i add a constructor to queue. I could stagger fleas. But that means the trouble of suicide-scouting. With 5 fleas, losing single one is a dent in vision network. With 15, losing 3, is not that great of a deal.
I am currently messing about with plates in skirmishes with AI, mainly testing it in 3v3 hard AI. Gaining personal flexibility of units for 150m is really nice. And while i was affraid that it would degrade Caretakers... No such thing. Plate gives 1-BP for 15 metal. Nano gives 1-BP for 22 metal. Plate cannot repair your riots, assaults etc. Nanos Can. Nanos retain their usefullness without metal income to match them, they only need energy to be somewhat usefull. Add in to the equation that nanos can reclaim in their range. If we stick to smaller numbers, nanos are outright superior, because you always should have more energy income than metal. And unit repaired is unit that gets "produced again" for energy cost only.
EDIT (way too late) - Yes. I just paid a bit more attention. Caretaker worth 180 metal is even more superior. Nothing of substance in that changes.