BTW: Working in manufacturing, I can tell you that generally speaking, the farther away a product is built from the designers and engineers, the more prone it is to assembly errors. It has less to do with the country building the product and more to do with the fact that the engineer is in Germany, and the assembler is in Mexico. When the engineers and assemblers are working under the same roof, they can workout assembly issues before they become consumer problems. And even if a problem makes it to market, Wolfsberg will likely have it fixed before Puebla does. In the mean time, a factory like Puebla may continue to crank out less than ideal products.
Now would this be enough to steer me away from a Jetta? Probably not.
With that said though, the Mexican made MK5's ARE slightly different than the German made MK5's. A lot of the parts, while interchangeable - use different materials or designs. For instance, I replaced the center AC vent trim on my wife's Mexican made Jetta with a German made OEM piece. The Mexican piece used integrated plastic clips to hold it in place, while the German piece used replaceable metal clips. I've also been told that the fasteners holding the cabin filter in place are different - although I have yet to verify that.