>>44730351More a buff to Ice-Types and Hail than a buff to Abomasnow, but I'll post Aboma anyway
Ice now resists Water, Fairy, Ground, Flying and Grass
Hail doubles Ice-Type's Defense, similar to how sandstorm doubles Rock-Type's SpDef
Hail no longer damages Fire-Types
Hail turns Water-Type moves into Ice-Type moves when it would be most beneficial, with the exception of Scald
More Pokemon (especially non-Ice Pokemon) gain abilities that abuse hail. Example: Stoutland now gets Slush Rush instead of Sand Rush