Hey Louis,
As Lawrence has indicated, "BOTH" techniques can provide sound weldments, although practice on thin material, especially aluminum, will render optimum results. For the custom polished aluminum diamondplate(.062) crafts I make, the corners are TIG welded using the "laywire" technique simply because of the thinness of the corner joint & the aesthetics needed. The corners are polished to match the material surface. Here are a couple pics to show you the joints & the finished results. I have never had a joint crack or break using laywire fillets. You will find that the filler diameter is the secret for a good laywire weld & on the thin corners, I use a piece of steel angle as a heat sink that helps eliminate any burnthru. Here's some pics....
Denny