No surprise here. He has mentioned before that to him, Yoona is the most beautiful, not just in SNSD, but the most beautiful female Idol he has ever met.
Those who don't understand will have to meet her in person to find out why. A fan I know used to never understand why Yoona is the prettiest, until she saw Yoona up close , and she was literally 'jaw-dropping beautiful',
and now her opinion is 'Yoona is the most beautiful in Soshi, period. ^^
And for those who think he is picking a safe choice or just following SM orders... really?
Its Kim Heechul you know?? , when has he ever 'followed orders' or picked a 'safe choice'???
he has always been honest and speaks his mind, whatever the consequences.