My statement about choosing a lugged frame may have been unnecessary, since the OP is talking about old frames. Almost all steel frames that I'd consider old would be lugged (yes, there are exceptions), but then again, how do I know what the OP considers "old?" To give an example of what I'm talking about: all other things being roughly equal, I'd choose a lugged frame from the early '90's over a welded frame from the mid '90's every time, and the reason is, for me, aesthetics. I have no way of knowing if the OP had thought about such things, or even if he needs to since he may very well be only looking at old lugged frames, but it was a passing thought and I thought I'd point it out. Who knows, maybe he likes the looks of a welded frame over a lugged frame? I doubt it, but either way I just wanted to make sure he realized there's an aesthetic difference.

And btw, the main advantage of brazing steel over welding steel is brazing creates a smaller HAZ, I'm not sure if that's what you were referring to earlier or not. And lugs do add structural reinforcement, although obviously very strong frames can be built either way-