What's so wrong about having a sexy concept?
Both show the same skin (there are some exceptions of course)
Both are marketed towards boys.
Both have sexy choreography (SNSD showing their goddess legs on Oh! 4Minute showing their gorgeous butts on What's Your Name?...)
Both use the sex sells.
The only problem I see is when a member isn't an adult yet, for example Girl's Day waited until their Maknae, Hyeri was 19 and then they released Expectation with a sexy concept.
Also it's a bit uncomfortable for adults to do a cute concept. Sojin (Girl's Day) is 27 poor her if she had to continud doing it and Taeyeon (Girls' Generation) has said that she feels uncomfortable doing it.
