Addandy- there are several different forms of certification. I am (was) certified for AWS D1.1 and Mil Spec 1595A. D1.1 is for structural steel with arc (stick), and is what you need for stuff like trailer hitches and building construction.. I would have to say it is more difficult to make a good x-ray quality weld with stick than with Tig, because the test part is 3/8" thick, and you have to put down several layers without trapping any slag.
1595A is aerospace quality Tig on aluminum, titanium, stainless, etc. I passed for position 1 aluminum, .030 to 1/8 thick. It is a butt weld with argon back gassing on a grooved backup plate, for full penetration without oxidation on the back of the part.
Becoming certified is cool, but they expire after a year. Its not really necessary unless you are welding professionaly and your job pays for it, imo.