User blog comment:Fliu/Chapter 989 Thoughts/@comment-30281369-20200907133003/@comment-30281369-20200908063633

It's not like the suit makes him invincible, so of course he'd be scratched up and bleeding; as King's attack was that strong. What the suit did though was offered noticable protection and mitigation against the attack, to the point where Sanji himself had stated that it annoyed him. It has nothing to do with selling base Sanji short over his raid suit form, it's been stated and shown that the suit increased Sanji's defensive capabilities with the added advantage of invisibility, so it wouldn't make sense for him to not use it, especially while they're at war with the Yonkos.

Also I'm of the belief that Sanji can match and best any of his brothers, with or without suits.