DDR is by far the better game. Better music, better arrow maps, and a better range of skill level accommodations. DDR has good arrow maps for beginners, and then there are maps that are basically as difficult as you could ever want. I used to be able to play most songs on expert and when I went to the arcade I would still inevitably get crushed by someone way better than me.

The pump it up arrows MIGHT be more natural if you dance facing exactly one direction all the time. In DDR you rotate your lower body often to get the most advantageous position. You're rarely parallel to the screen so it has never felt uncomfortable. Basically, you'll be moving your whole body a lot, which to me feels a lot more like dancing.