dave1949
Super Star Member
One difference is, when tacking or welding the two pieces, you have doubled the amount of metal that has to be heated/melted to get penetration in both pieces. You asking more from the welder in that case.
I was able to get good penetration with my practice beads on the 1/4" thick metal as you can see below. Ignore the first bead on the left. It was made with the highest wire feed speed setting.