When you run below script, you will receive email with csv file with CRUD permission comparison.
You need to specify the target org domain url and sessionid or access_token of target org and need to run below script in source org in execute anonymous window in developer console.
Below is script:
Below is snapshot of csv file:
This is just a prototype and it may work for small organization. You need to consider heap size and apex CPU time limit exceeded errors. You can refractor this code for your use based on number of objects that you have in your org.
Hope this will help!!