Twice the Ice is most reliable, & most expensive, but some people don't like their "broken sheet" style ice.
Kooler is 2nd best known & pretty reliable. Good Scottsman Ice makers w/ few issues, unless you have poor ice quality. Then, Id suggest plumb it from your SDR inside w/ a lp pump to come on when solenoid opens at ice maker.
Id DEFINITELY buy used, as they're less than half price & can be found all sizes (if you're patient).
If you can get a restaurant or 2, u can make very good $$.