I see those all over the place here in Osaka, but I've never tried 'em out. The Dragon tanks are well-detailed, but the Digi-Qs are scrunched up little munchkins. Looks like they'd be a blast to play with, though!
They have big Digi-Q combat meets at major shopping centers throughout Japan!
Here the Dig-Qs are about 5,500 yen and the Dragons are about 7,500 yen, I think.