A bearded dragon that is not active is a dragon going down hill. We were looking to get a 2nd reptile last month and went with a dragon. The reptile store said that the colorful little guy that I picked was jsut resting. I believed him and took the little guy home. He lasted only a few days, never ate once. I went back to the reptile store and showed them pictures of my 4 foot long tank. These pics also included the theromometers at each end of the tank showing 78 degrees cool side and 105 degree basking spot. They said everything looks great and that my setup was perfect. I then pulled out the dead dragon that I got the week before and asked them to explain how this guy could have passed so quick if I had a perfect setup? They quickly stated that if he was not active then he should have never left the store. They replaced him with another one that they made sure was eating and active before I left. This new dragon is ALWAYS alert. He seems to know everything that is going on around his tank at all times. As soon as food jumps into the tank he is bouncing all over the tank to chase it, all day every day.
Sorry for the long post. I just wanted you to have an idea what to look for if you do get a dragon. I had a very sad learning experience that I would like to help others avoid. Ours is very nice, and very funny. The stuff they do will keep you and your little one laughing. Dragons are gentle and mine reaches to be held any time my hand is in the tank.
I have no experience with snakes so I can't say that either is a better choice. I can only give my experiences with our baby dragon. Getting the baby was the way to go for us. Its fun to watch them grow. They grow faster than out chameleon, and are so much easier to take care of.