You really think its a smart idea to take a rarer animal from the wild because its just "rare"? Your comparison doesnt apply to this dialogue because youre comparing two animals that are captive bred here in the United States, the fact that Australian H2O dragons arent offered for sale as much as beardeds does not make them more RARE, it just makes the bearded dragon more popular.
Both species are illegal to import into the United States from Australia, so what you see here is what you get. No collection trips no importation nada. Now if you compare that to other animals that were suggested, that are indeed being imported they in fact could be rare, not in the sense of marketability, but in terms of their origin ie, habitate locality etc. That is where your duty as herp-hobbyist is to not just get one individual. You should definatley get a group or guaranteed pair so you are not inhibiting any further on their importation, you then become a valuable asset to the the hobby because you are attempting to breed them in captivity.
This is why I always suggest that if people want reptile pets, that they go and get readily available cb animals.