(Judge Even If You're Not A Fan) Best SNSD Member to Duet With Taeyeon?

Tiffany or Sunny

Vocally Taeyeon and Jessica voice surprisingly gel very well.

But overall and performance wise it's easily Taeyeon and Tiffany. Their chemistry has always been unmatched and was easy to see during TTS.

Seohyun because I want to hear her singing again