Based on your "basic/general" knowledge on these two, I would reccommend a bearded dragon for first timer. Iguanas are just too big and work-intensive for beginners. You need plenty of time, space, and even money at times to keep one properly.
Beardeds grow relatevely small compared to igs, around a foot or so, maybe a bit more. They tame like babies when done right, eat a variety of veggies and insects (crickets and meal worms are better) and need less space for an enclosure than iguanas. However, they still need a cage about 4 or 5 feet in length, 3 or 4 in depth, and 3 or 4 in height.
Do remember that the dipsosaurus (desert iguanas) are excellent pets, and reach a size of 14-16 inches. Cage size is about the same as beardeds as listed above.
If you need any more information, let me know. However, as most here will agree with me, the #1, top first reptile pet anyone could have is the gorgeous and adorable leopard gecko.
There is a metric ton of information on the web and in literature on these guys, and they are very long lived!
Let me know if you need more info.
-IJ