Do note that they both rely on (included) cartridge converters.
That's probably one of the biggest things to me: having different filling systems. As I mentioned in the article, I have piston fillers, vac fillers, etc. I wanted to have Parker 51 clones that use the Vacumatic system.
I am surprised that you were disappointed in Jinhao pens,
At this point, I think the only decent one I have is the x750, and even those have an issue with the cap wobbling (but at least the seal still seems to be good). I've had at least a dozen other Jinhao pens (not just Parker clones), and they've consistently had issues from scratchy nibs to bad seals.
In contrast, Wing Sung and Hong Dian pens have never quite matched my expectations from reading online reviews.
These are the first Wingsung pens I've managed to get, so I can't say anything beyond this experience. Hongdian OTOH, I've not had an issue with. I have four M2s, two Black Forrest's, and a pair of C2s, and all have been exceptionally high quality. I would almost prefer the M2's over my Kaweco Piston Sport pens… But the Piston Sport is a piston filler, which I like over cartridge / converter pens.
One of the things I've noted is that many of the Chinese manufacturers have had inconsistent quality control, especially a few years ago. In particular someone pointed to Asvine pens they bought 1.5-2 years ago as having issues. It seems that in that time at least some of these companies have improved their quality and/or quality control.
But, I've also noted that many of the sellers on Amazon won't specify when the pen they are selling was released. It's possible that the Jinhao and Junlai pens may have been from a few years ago, and lack the quality control they have now. (But, this is completely a speculation.)