I used to be in business with a retired Mechanical Engineer, we modified a few mills and were in the process starting a company converting them to CNC.
Many of the sub $1000 mills are all made by the same Chinese company Seig,
The ones you find at Harbor frieght and Grizzly and other are all made by Seig, but there is a difference.
We were in talks with Seig to import them directly from china and then we were going to modify to CNC and sell them to hobbist etc.....
well before we got to the marketing my partner died suddenly, he was the money man etc, but I still have two of mills, and my dream of being a importer was dead.
But, I learned a ton of stuff about these small mills.
I like the Grizzly brand the best for two reasons. but first let me explain how Seig sells them.
When you are buyer like Grizzly or Harbor Freight, Sieg gives you options on the the Guides, bearings and motors etc, they usually offer 2 or 3 levels of quality.....
Well as you know, Harbor Freight buy the cheap end and Grizzly asks for the better guide, motors etc,,,,yes the cost more, but its worth a few dollars more.....
Grizzly is my choice because:
1. They choose a higher quality parts from the manufacture
2. Also, Grizzly carries parts for every machine they sell, in stock.....Harbor Freight and others don't...
The mills used to come in three models X1, X2 and the big one X3 I have the X3....they now make a couple of bigger ones....
I know of knife maker who had a X2 that he modified and made all kinds of parts (He bought the cheap Harbor Freight and did fine)
he even cuts Titanium with his little X2 he modified to CNC.....
He has since upgraded to a TorMach mill because he does a lot more production now....
https://www.youtube.com/channel/UC8SC-01ZKmzTIa2Usn6fexQ here is a like to his YouTube Channel, he has 214 Video and if you go back about a year or so he gives a ton of good machine tips about his X2
Well that's my 2 cents hope it helps
Pandaman