How is the different between the 'Create → Alert' option and advanced search alert?

The 'Create → Alert' option is like the advanced search alert process, but less customizable, and therefore less specific to exactly what you're looking for.

It's easier if you're looking to set an alert with one click, but with ample articles available on how to create searches, (especially super specific ones using keywords searches), advanced search can be just as easy. 

If you're looking to avoid an overwhelming number of email alerts, 'Create → Alert' might not be best. See here for steps on how to create an alert based off of an advanced search.