Originally Posted by Scooper
I think you're forgetting the strength
added to a brazed lugged joint by the lug itself. There is
objective evidence that brazed lug construction is stronger than TIG welded construction. While the testing at U.C. Davis was done before air hardening steel tubing like Reynolds 853 was available, the argument regarding stress risers in TIG welded joints making them more prone to failure is still valid.
That blurb from Spectrum is full of inconsistencies. For example regarding the UCD study, first they say "They concluded that all three joining techniques (TIG, Lug, Fillet Brazed), done properly, are clearly of sufficient strength for the purpose of bicycle frame construction." Next they go to say, "Frames built with silver soldered lugs will last longer than those that are fillet brazed and considerably longer than those that are welded."
Honestly, the joining technique does not matter as long as the joining is done properly. TIG is very popular since it's cheapest. It's also slightly lighter which is important to many people. Frame will ride the same either way - it's mostly about looks and cost.