Generally the more hobby orientated machines are quite compromised design wise.

The biggest factor is probably how much accuracy you need?
Generally they're quite a flexi design (unsupported rails), single ball screw on the long axis, and cheap ball screw retention (usually a couple standard bearings preloaded, or two basic thrust bearings. Some even just rely on being rigidly coupled to the stepper motor).

Then there's the electronics. Often cheap drives, cheap controller (if USB, probably with non-existent support).

They can be made to work reasonably well as long you're not expecting micron accuracy, perfect finishes, and don't push them that hard, but long term reliability can be challenging.