Each of the 20 human/mamodo pairs has about 5-7 different spells to use. Some characters have special affinities to certain types of spells (Kiyo and Zatch favor lightning attacks, for example), but they'll all use up-close, ranged and barrier spells before the day is over. They're just different enough to please the anime fans, but perhaps not those wanting a deep fighting style.
But then again, non-fans probably aren't going to look twice at Mamodo Fury. This one's obviously built just for the screaming-blonde-hair-guys crowd - evidenced by the full backing of the show's voice cast and a story mode that follows the series. If you know what you're getting into, there's probably plenty to like about Fury - we'll know for sure this summer.