Since the above vendors margins are probably better, than the low cost providers, they provide good service, at least in the case of LMS. They have provided me a couple of parts gratis, including an apron gear and paint for my 7x16. Generally, they are very responsive to questions, and maintain a lot of parts in inventory. Fit and finish may be better. I still use my 7x16 for some operations over my 10x22, since I have yet to adapt some of my tooling for the larger lathe. My spindle bearings were very good and the lathe spindle has sub 0.0001" TIR. The parts that LMS sells really do fit, I've never had to modify any of them. The LMS lathes allow inch and metric threading which is not common for the low price offerings. The cheapos do metric only.
For my 10x22 Grizzly lathe, that I purchased used, I have found parts are still generally available from Grizzly, but that model is still current. However, the replacement parts were definitely not the same quality as what my lathe came with, the finish was inferior and needed work to go into service.
Personally, I wouldn't go for the bottom of the barrel stuff, unless you are pretty good at machining already and have experience fixing marginal designs. The super cheap stuff sort of works, but it's area of operation is even more limited than the already diminished capability of the mini-lathe platform. To bring the low end stuff up to snuff (if it is possible) requires a level of inventiveness and creativity that many do not possess. If you do have that talent, by all means go for it.
I learned a whole lot on my LMS 7x16, it's both capable (if adjusted properly) and limited (due to it's basic design). I don't regret my purchase one bit as I got a whole lot out of it.