^
But please keep in mind that STEP done much better digitally. SNSD have more hardcore fans in Japan, but Kara has more public recognition. And just maybe another reason is STEP is included in Super Girl tracklist, which affected the sales of STEP.
Plus, there was a lot of Kara releases during the time frame, Winter Magic + All About Beauty + Super Girl + STEP, compare with the group you just mentioned, they only have a Korean album and Japanese tour DVD (released in late of Nov).