it's a give and take, the cards with no attributes have higher stats across the board.
not always the case. an example would be rem and yoruichi. both are 1 star. rem has attributes and yoruichi does not but at the same level, rem still has higher total stat increase than yoruichi by 1%. and in the case of the same card with different colors, stats don't change whether it has an attribute or not (same level).