"-라고" and "-다고" are used when we quote what sb has said, and they are also called "the reported speech" in terms of grammar.(sb = somebody) "보고싶어" 라고 is more like "direct speech" with the quotation mark while "보고싶다고" is referring to "indirect speech"^^/ As the direct speech, the first one will be ... She/He said "I miss you" = "보고싶어" 라고 말했다 As indirect speech, the second one will be ... She/He said she/he missed you = "보고싶다고 말했다" \^o^/

The first isWrong usage