に[限「かぎ」]って／に[限「かぎ」]り

According to the book I am using, [完全「かんぜん」]マスター, "に[限「かぎ」]って" is rather subtle and complex. It can have undertones like "exceptionally", "right at this important moment, this bad thing had to happen" or, as exemplified in the sentence "うちの子に[限「かぎ」]って", may express full trust in something or someone.Also, に[限「かぎ」]り is rather formal, whereas に[限「かぎ」]って is used in everyday language.