I'd also say that two identical bikes that are lugged vs. tigged, the tig frame would be a bit lighter, but once you hang parts on it, you wouldn't be able to tell the difference.

Functionally, there's no difference though that I can tell. The steel used is a much better indicator of ride quality than the joining method. Further, I'd argue that riding style and rider weight would also make a huge difference. Something that is really stiff and snappy to a 120 lb spinner would be weak and willowy at 220lbs and mashing...