I own both a Mali Uromstyx as well as a Bearded Dragon. If you want something larger, you should probably go with the Beardie. Most Uros are not that large, probably averaging about 12-14 inches as a adult, including the tail. The only Uro that gets large is the Egyptian Uromastyx of which there are 2 subspecies. Only one of them can get up to 3 feet, but accurately identified ones are somewhat hard to come across.
My opinion is Uros are easier to keep. They do not require any live food items ever, unless you want to give them a few bugs occasionally. 95% of their diet should be high quality greens (collards, mustards, dandelions) with some fruit and vegetables mixed in, fed daily. However, Uros require higher basking temperatures and a flat enclosure. They do not climb so floor space is more important than height. UVB is absolutely necessary. Those tube lights need to be replaced at least once per year since they stop producing UV even though light still comes from them.
I believe Katieasaur was correct in that Uros can be more flighty and may not take to handling quite as well as beardies. That being said, they can be trained fairly well by hand feeding insects and greens. If the time is taken, they can tame nicely. With most animals, be sure to get a captive bred juvenile. Many are wild caught in africa. That is something that is not a problem with beardies.
Uros come is several "styles," much like beardies, but I believe uros are more colorful. Red, orange, and yellow bodies are easy to come by and can be quite pretty.
Hope that was at least somewhat helpful! Happy searching!