Look thru the RCM archives for more info regarding the mini-lathes (also mini-mills). Another resource is
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There are considerable differences in the number of accessories that are included with some models.. faceplate, tailstock chuck, steady/traveling center rests for long workpieces etc.
Almost all models have plastic change-gear sets, and plastic gears in the headstock, too. One or 2 more expensive models have "metal" gears, possibly steel or cast iron, but maybe just potmetal gears (the sellers don't seem to specify which metal).
You will likely want to get many other accessories/tooling items, regardless of which model you choose.
The headstock spindles have an MT3 taper (same as 9x20" models), which can be adapted to 3C for collets that are a feed-thru type (secured with a drawtube instead of drawbar).
The minis are lightweight and compact, which are definitely desirable features to many users.