First of all, you need to define what you mean by very best. Second, you need to figure out what makes a defender a better pick over a Corr. Finally, Corrs get FS at 30 now. This means in reality they have it at 24 when exempt. This means any Yin level TF and above a Corr will have it. Defenders will have it for Synapse. For SB, a Corr would be missing it on Posi 1, so yeah.
The advantage for a Corr is simply in the rain/DoT powers. Also, the debuff aspect is going to be better for a Defender. For me I would look at three sets as a starting point. Sonic due to the -Res, Beam due to some -Res and -Regen, and Rad due to the -Def since Kins need to hit. There are some others ones which are nice mind you. DP plays well in melee where Kins tend to live anyway. Elec can do some sapping and Transference added in. If I absolutely had to pick one, Kin/sonic.