Honestly, i don't like the whole comparison thing between SNSD and KARA even though it isn't that unhealthy, but yeah.
Sales > Rank. SNSD has various big competitors releasing on the same day as them, not forgetting they're rookies as well.
I think we should just be concerned with KARA's sales. They're doing great as rookie right now, and hopefully it continues. I hope their next single will outsell their current debut single. If they don't, even if they had a great debut sales, it won't be considered as a success imo. Titles are nothing, progression and final outcome are the most important factors.