That means you are getting two entirely different products, BKK-VIE is a Lauda Air flight meaning EXCELLENT FOOD and crappy seats ("Amadeus Class") , whilst VIE-JFK is an true OS plane, meaning GOOD FOOD, nice seats and so-so service ("Grand Class"). However, VIE-JFK and VIE-KIX are about the best routes in terms of seat and service. It doesn't get any better on OS.
Check airliners.net for pics. Oh, and there are loads of threads in the LH Miles and More forum that answer your question.