I have a couple of Chinese machines - one had DSP, the other had NC-studio.
I've replaced both controllers with mach-3 because I was seeing dwell marks and odd artifacts in the surfaces.
If you're just profile cutting MDF they'll probably be OK but maybe not for fine detail on 3D shapes. I cut scale model parts from acrylic with endmlls between 0.6mm and 3mm so smooth path interpolation between goto's is essential.
Here's an example of a part cut with a JX-1212 machine controlled with NC-studio (on the right) vs some parts cut with mach3. The middle part was cut on the same JX-1212 machine after converting from NC-studio to mach3.
I'd suggest buying an NC-studio machine and, if necessesary, convert to mach-3.
From a usability point of view I find being able to see the toolpath and tool position on the PC screen pretty useful when setting up a job.