How to compare two web sites in different ways?

I'm looking for solution for comparing two web sites and check difference. And for now I have only two ideas. It's need for checking web sites after migration from old server to new server(mostly wordpress cms)

1) Getting content from main page with curl and check difference. Or getting status code with curl and check it.

2) I think it's not good idea. I can make a screenshot of main page(with python script) and after migration make a new one and compare them with python script again.

Any ideas? How to compare same web page before and after migration and make sure that everything is working?

Thanks!