There is a good set of articles on the metalurgy of brazing here:
http://desperadocycles.com/Lowdown_On_Tubing.html
Apparently a silvered joint is weakened at the joint and some 10 mm further, while a bronzed joint retains most of its mechanical properties at the joint, but is weakened in a region 10-30 mm passed it; you need more butting.
Here is some data on TIG vs. fillet:
http://www.bobbrowncycles.com/eng.htm
seems the short HAZ of TIG is still quite strong but perhaps brittle.
But that's if you're skilled enough to apply the minimum amount of heat possible.
Gas-welding would combine the high temp of TIG plus the long HAZ of brass. Probably okay if the butts are long.
Edit: I'll add that welding is technically harder. I tried a bit of gas welding. To get a properly penetrated joint, you have to straddle the point at which you're blowing a hole in the tube... though...