I've owned both, taken samples, and can see no difference in image quality. The more recent Chinese-made 1.4 bodies do feel alittle cheaper in quality, but I'd say the glass is equal. Bottom line: don't sweat it.
Oh, one more thing . . . the body quality difference on the 1.8s seem more noticable - with the older Japanese-made bodies being better. If memory serves, the older 1.8 Japanese-made bodies are metal, not plastic, like the current versions.