Girls' Generation one part of my favorite K-Pop acts. Where do I start as stated before their evolution as a group is really outstanding as there has been actual growth these last 3-4 years. They are the biggest girl group in Korea and IMO rightfully so even though I know many people don't agree.
Album: Now speaking overall their Japanese album is by far and away their best work. Girls' Generation the album is a filler-less masterpiece that I wish could have been promoted more. When I say promoted more I mean in a more Western way a la multiple singles, videos, performances,etc. Now their Korean albums are hit and miss but their best one would have to be Oh!+RDR IMO.
Mini-Album: HOOT!! Bitches slayed with this mini. All the songs slayed minus that Snowy Wish tragedy. This mini also contains their best song EVER
Title Track: Has to be between 'The Boys' and 'Gee'. The Boys just completely ***** no explanation needed. And the impact Gee has had in Korea is also self explanatory and its so damn catchy.
Performances: There best performances are definitely from this whole year. Starting with their Japanese tour. Even though they didn't sing for some songs The performances themselves were amazing. And all the performances of 'The Boys' are phenomenal IMO. Showing they earned the title as Korea's favorite girl group.
Style: Toss up between the retro 'Hoot' look and the sexy sophisticated 'The Boys' look
Overall their best era is hard to pick because each one has its ups and down. I think I'll have to go with Oh!+RDR era since 'The Boys' era has been a meeeeeeeessssssss promotions wise.