Well, I have never heard of Sites before so I had to do a little googling before I could reply.
It seems to me that google sites is more of a website for information sharing or directing via links.
1) Google classroom allows for submission and grading of student work, I did not see that with Sites.
2) Google classroom allows for interaction between the teacher and students and students with each other. I did not see that with Sites.
3) Google classroom allows for emailing parents in a single click separate from students if that is the wish. i did not see that with Sites.
Sites did not tempt me away from Google classroom.
It seems to me that google sites is more of a website for information sharing or directing via links.
1) Google classroom allows for submission and grading of student work, I did not see that with Sites.
2) Google classroom allows for interaction between the teacher and students and students with each other. I did not see that with Sites.
3) Google classroom allows for emailing parents in a single click separate from students if that is the wish. i did not see that with Sites.
Sites did not tempt me away from Google classroom.