it's up to personal tastes, don't you think?
the way you're asking is as if you think there's only 1 answer to this question when there's not

are you asking about whose technique is the best? who has the best control over their voice? who hits all the notes the best?

powerhouse doesn't automatically mean a flawless singer and a calm, gentle voice doesn't automatically mean a bad singer

jonghyun and kyu for me, their powers are the best!