How to evaluate the singing skills of iu and Kim TaeYeon?

I think each has his own merits, and both of them are good singers. However, it is 20 18 that questioned IU's singing skills, so no one should show off his voice. I can't play three high notes, which is very different from ordinary singing. It's easy to pronounce high notes, but it's hard to last that long. Maybe, but it's hard not to spoil for so long, it's hard not to spoil. It's really not difficult to sing to the names, especially to the names, after listening to the live night letters. She can also express her feelings to the extreme, making foreigners choke when they read the translation.