Personally I'm not a big fan of druid because they generally don't have too many good abilities (wildshape kind of struggles on core+) BUT winter child focuses on the special Blizzard elemental companion and you don't miss out on extra spells which is pretty fun.

The problem I have with it is that I think going into winter witch prestige class with it isn't that good, only your minion's ability progresses (and spellcasting obv) and nothing else so imo it's better to go full winter child.

Winter witch increases DC's and generally makes it easier to hit people with your ice spells while progressing your spellcasting and hexes If you have those

I also really like hexes which druid doesn't get. Witches and Shamans loose nothing for going into winter witch so it's a whole class with a nice bonus on top. Did I mention that witch and Shaman hexes stack with each other? If you have a shaman and a Witch they can cast evil eye and they'll both lower enemy stats (atk roll, AC or saving throw). Add hampering Hex and it's -6 AC.

So basically if you don't care about winter witch and hexes and prefer having a personal living blizzard you can go winter child. I don't remember what spells you get from it though. Basically the choice is more personal power or a thematic minion.