Gas welding is a very much effective and sadly lost art. Most of us wrench wranglers are pretty good at scabbing together exhaust systems with the old blue-point wrench and coathanger wire from the uniform closet
That's where MIG shines for me- building exhaust systems without 27 unions, couplers, reducers, 157 clamps and enough tags on all the pieces to pose a serious fire risk the first time you start it up! MIG is real nice on clean exhaust metal. Lots easier than stick, for me a least.
Brazing I'm a whiz at, the result of years in a body shop back when brazing was all we had. Gas welding? Ehhhhhhhhh, not so much. I still have the first Brownells bolt handle I tried to gas weld to a Mauser bolt with Brownells super duper expensive aerospace rod. It still looks like someone had a terrible accident with a tiny bumper jack handle...