Well, I guess 3 semesters will give you more time, but the amount of study will be almost same. But, you are right because you will learn/study more thoroughly with 3 semesters.
And, as you said, internship will give you a real world experience about what you're learning. But, that is what internship is. You will have the same experience whether you graduated or you have one more semester left. I just don't understand why people try to distinguish between a summer internship in between semesters and a summer internship right after graduation.
Agreed but doing an internship and then being able to return to a classroom is a great thing to be able to do. It gives you time to digest your new practical knowledge in a safe academic environment and also gives you context within the classroom.