I would have to agree that they are both valuable. GTAW might be the more difficult of the two to master for most but both are a skilled process. Having said that, GMAW is also very valuable, and is also a skilled process for the welder that is serious about what he/she does, but it is also, imo, the easiest to master, but a good skill to have if you are looking to be well rounded in this industry. GTAW was the hardest for me.
how bout a TIG pipe welder? that's the best of both worlds. remember, one pipe certification will cover you for all of your structural certifications using the same process. learn stick welding on pipe too.
it's kinda like getting a motorcycle license, but no regular driver's license...yeah, you can go places, but not everywhere. and besides, you wanna be the guy in the company who can say, "Yeah boss, I can do that," instead of "Well, I've done a little bit of that, but I'll need some practice."