I wouldn't say she the best in the whole group but id say shes in the top three next to Tiffany and Taeyeon But who am i to say, everyone has their different opinion :)
Tiffany once told Jessica: "Dude, do you know that you like singing and you don't even know it?" So, yes, obviously Jessica is good at singing and that's why she's one of them main vocalists. However, she obviously isn't very interested in it as she didn't participate in SNSD's first sub-unit TaeTiSeo (the members themselves stated that the only reason a sub-unit was formed was because the other 6 members were more interested in other stuff).
Taeyeon also gets the most lines and high notes, even though Jessica can do great high notes. I have to say that I've always thought Taeyeon's voice was the best, and Tiffany definitely has a uniquely husky voice that I adore. Meanwhile, here's a compilation of Jessica's high notes!
I am sure Taeyeon is the best vocalist in SNSD.SIca is great too and that is why she is a main vocalist.But Taeyeon is lead vocalist and every OST she sang became a big hit whic prove Taeyeon is the best vocalist.Eg If and Closer OSTs
