this is ranking of best dancer in snsd .

Ok let me see if I can make some sense of this. Is Sooyoung a better dancer then Yoona... I can tell you its a matter or talent versus passion for this type of question. I think Yoona can dance better than Sooyoung, the problem is Yoona as of late is a bit seems a bit behind form her usual energetic feel when she dances.

Sooyoung is a bit stiff so a lot of fluid movements in choreography she may not be the best at the only exception I can think of is her "Sway" video, which is a rare occurrence.

I want you to look at paparazzi, their latest video. Yoona is a a bit more "fluid" in her dancing then Sooyoung, but Sooyoung as of late is putting more energy into her dance. The same thing with Sunny vs Seohyun.

Though Seohyun is a better dancer, she is ranked lower then Sunny because Sunny puts more energy into her dance then Seohyun. However that does not mean Sunny can dance better then Seohyun. The same Sooyoung may put more energy into her dances lately which will put her at a higher rank, doesn't mean she is a better dancer then Yoona.

technically i think yoona is better than sooyoung- and i think that is why she is the lead dancer with yuri. but sooyoung put a lot of emotion while dancing. unlike yoona who has the same expression throughout the performance.

that actually depends on the performance and which dance is more suited for each member.i've seen some performances where only Hyo, Yul and Soo are included, but not Yoona. and for example, when all the members are dancing, they usually let HyoYulSoo do the most difficult parts. for example at "sorry sorry" (0:40)
link

besides, if you notice, the new dance ranking is very recent. they used Yoona more in the PAST , where the ranking was different. they puted Yoona at third and Soo at fourth. .
now, that the dance ranking has some changes, you notice a lot of differences on their recent MV's. Sooyoung is a lot in the middle and front, since "mr taxi". of course Yoona continues to be more at the front but that's because she's the face

Yoona Is Better than sooyoung

mmm.. i think yoona dance better than sooyoung, but people opinion can be different..

because i also say, hyoyeon is best dancer, but i like yuri's dance more ^^