My criteria is:
1. Do I have room for it?
2. Can I easily buy bobbins and find the right size needles for it?
3. If I am going to use it as an electric machine (not a handcrank or treadle) what do the wires look like?
4. Is it pretty? (I like to have good looking machines around me, not something so scratched up that it will take major work to beautify it.