>>20431533water/fairy leaves it with an all around great and fairly unique typing. Better than water/dragon in the amount of resists it has, but has all the weaknesses bar steel of both.
water/dragon only has one weakness to dragon, but lacks a lot of the resists that water/fairy brings. Being weak to something that you conversely beat with STAB isn't nescicarily a bad thing for a defensive pokemon, but the speed might let it down.
Six to one half a dozen to the other imo.
