Keeping them - essentially the same. The same kit requirements anyway and although a 4ft viv is the usual requirement for an adult Beardie, it would be terrific
for a Rankins.
As you'd prefer to re-home (
) Beardies are far far easier to get (getting a Rankins when you want them can be surprisingly difficult - even to buy "new"), there are some terrific animals that really need a new home and you'd definitely be doing a good deed by taking in a Beardie that some kid has got bored with. (Not a general dig - I know we have some excellent and responsible young animal enthusiasts on these forums.)
Another reason for Beardies so often needing re-homing, is that people will keep getting two "to be company for each other". They then get dominance issues and the animals need separating.
Wild Bearded Dragons are solitary, coming together only to mate. Another dragon in their viv is just a competitor or something to be harassed to mate - not a "friend". Just get the one to lavish attention on.