I think the thing about quality difference between an SX and, say, a Fender, or even between an MIM Fender and an MIA, is really just in the QC. They're all using alder and maple (or whichever woods), nickel, steel, and copper wire, and they're all using pretty similar schematics for the CNC machines etc. So theoretically, yeah - there's no particular reason an SX can't be just as good an instrument as an MIA Fender. But what the difference in price means is that the SX goes through the mass production line a bit faster with less checking for detail. If everything works just right, it will be a great instrument, but there's higher odds something won't be quite right and the problem won't get caught. You're more likely to get a lemon. That's the only reason I can say that some people say they're "junk" and others say they prefer them to their Fenders. It's the same difference between MIM and MIA Fenders; not that American workers are better than Mexicans (there's the old joke anyway, that MIMs are made in Mexico by Mexicans and MIAs are made in California by Mexicans), but that Fender uses the American plant to make instruments a little slower with more attention to detail and uses the Mexican plant for faster mass production.