1. Serious: Taki's gameplay revolved around locking down opponents with strings that shifted into PO and baiting them to try to interrupt a frame trap, mixing up cancels with full strings to always keep them guessing. Natsu relies on fishing for counterhits and then getting big damage off her long combos. I don't dislike the new style, but it's not the same. She has PO, sure, but it's not used in the same way as Taki used it.
2. Casual: Taki was a badass ninja babe. Natsu is some weeaboo animefan's wet dream. Her backstory may have well just been stolen from that stupid anime cartoon. When I looked at and listened to Taki, I could believe she was a ninja that hunted demons. When I hear Natsu, I feel like I'm passing through a crowd of teenagers coming out of Hot Topic.