unless your beardie is no more than 16" long, it will be too hard for him/her to turn around. from what I've heard, the male beardie's genetalia (don't know what to call it) is in the base of it's tale, so whenever they are forced to turn in an area that forces them to bend their tail, it sort of constricts the lizard's genitals. I haven't done enough research on this, so I would like to see how much of a difference this would make between male and females.
Also, since the other tank isn't as deep, it will make the beardie feel like the equivalent of a person living in a hall way. Ideally, we would all have 4'x2'x2' cages which give the benefit of length, and allowing the lizard to turn without the ends of it's body touching the glass. I have a tank that is 36" long 18" deep and 25" tall (I upgraded from the same size as you) which works out well because my beardie isn't even 18" long (yet). This also gives you extra height to build a better basking site. Had I had the space available, I would have gotten something 4' long, but at the current time I couldn't fit it nor do I require it.
later