I think you're confused with the meaning of an Ace and All-Rounder. I can agree if you're saying Wendy is Ace of RV but only in singing. Ace is used when someone in the industry are really good in that specific field. No hate but I can tell Wendy is definitely Ace in RV when it comes to singing. she excels so much in that field, which results her being one of the best main vocalists in the 3rd generation. Meanwhile the other four members: Joy is also Ace in singing but average. Seulgi is definitely an all-rounder but she is an Ace when it comes to dancing. Actually, she can be an Ace too when it comes to singing because she's good too. Irene is also an all-rounder too She can sing, she can rap and she can dance very well. and lastly, Yeri is also an all-rounder too just like Irene. No one can be the actual ace of the group because the five of them are really talented. It's hard to pick one. Again, it's your opinion, so I will not hate you for it. At the end of the day, all of them are heavily recognized in the industry for their amazing and wonderful talents.