Collets are good for boring because it gives you much less runout, which makes it easier to true up the barrel. A 3 jaw probably wouldn't be too popular with barrels because of their runout (at least IMO).
Don't quote me on this but at 220V, you use less electricity (cheaper to run) than 110V, I read that somewhere but never confirmed it.
Benefits to 3 phase, read this I would say to start What are the advantages of three phase to single phase electric power distribution systems
And to make this post legit...