Hi MIke here. I am a welder at a production plant, and tig welding to me is better because of the penetration that you can get with very little or no filler rod. If the heat is right, you will heat up a very small area, and I have never seen a brittle joint yet. also if I were doing it I would purge the lines with argon to ensure total penetrartion. Mig welding would be my second choice. Now this is just MY opinion, I'm sure that there are others who would feel the opposite that I do. You would have to do what would be most comfortable for you. Nike