Join Date: May 2010
Location: Long Island, NY
2011 Elantra PZEV 6AT
2011 Sonata 6MT
Mentioned: 6 Post(s)
Quoted: 126 Post(s)
From what I could see during my car shopping, the only differences are the colors and brands of tire installed. The Ulsan cars have slightly different colors (Titanium Gray vs Alabama's Harbor Gray, for example), and the Ulsan cars have Hankook tires while the Alabama cars have mostly Continentals.
With Alabama running at full tilt since late last year, any early production issues are probably addressed by now, and so I suspect there is little if any difference in parts/build quality between the two plants.
As you found out, Blue Sky seems to be Ulsan-only, and I am pretty sure Red Allure is as well. Desert Bronze is Alabama only. I did notice the two blacks, the two whites, and the two grays - one for each plant.