1. Hyoyeon. She definitely has the most technique and dancing seems to come naturally to her. If her dancing has a flaw, it's that she can be too aggressive in her movements which can sometimes look a little weird. She's still the best, though.
2. Yuri. Though she hasn't really been improving, her dance moves are still very smooth and even when she messes up she is confident. But she doesn't show that she can do different types of dancing.
3. Yoona. Yoona is always very controlled in her dancing. Her movements are sharp, clean, and quick. She rarely messes up and never misses a beat. The problem is she is almost too pretty and cute for some dances. She always wears a smile even if it doesn't fit the concept.
4. Sooyoung. She dances very gracefully. She always looks comfortable and confident when she dances. Plus, she's tall and thin and her legs are really long so it's interesting to see her dance. But sometimes she can look a little sloppy.
The truth is, Yuri, Yoona, and Sooyoung are actually pretty close in skill. If they worked harder they might be able to get to Hyo's level.