I don't really know. Conceptually welding is the lightest, then possibly silver brazing, then brass, then lugs. But I don't know the real answer because the tubing world was set up originally for people making lugged bikes, so the stock is designed around that use. There are also comon practices that would favour one or another. For instance welded frames often use a heavier head tube, but it isn't required. So which is heavier the possibility or the actual practice.
I doubt the differences will mater to you if you are considering a steel frame in the first place.
I've read contradictory statements saying each one is heavier than the other, so I'd like to know what's true.
Do you have to use thicker-walled steel tubing if you're going to braze, thus increasing weight? Or can you use the same tubing for either style?
Personally, I like the brazed look a little better than a lugged frame, but I could go either way when I build one. If one style is significantly lighter, though, it'll win in the end.
It sounds like you haven't built a frame before so I'll say this- building the lightest frame possible shouldn't even be a consideration for your first frame.
Just pick a joining method that's compatible with your tools/skills/aesthetics and go for it!
No, I haven't built before, but I'm also not going for the absolute lightest. My current welded steel frame is 5lbs, so as long as I stick under that, anything is fine with me.
Aaron, I just finished this 61cm lugged frame yesterday. In fact, I'm still soaking the flux off. It's nothing special; it's built with Nova Supply generic double-butted .8/.5/.8 OS 4130 chromoly steel tubes and investment cast Long Shin lugs. It weighs 4.18 pounds.
Considering the size of it, that's a pretty good weight. I ride a 53cm, myself, so I could probably hit the 4lb mark before paint, which typically adds a quarter-pound or so. Could you link to where you buy your parts?