How to handle remote validation Add and Edit form

Question

Hello Sir/ma'am,

 

My question is, which one is the best method or concept..

When I'm using remote model validation both time Add and Edit form.

I'm using system generate key with First Free Number.

So do we need create separate model class for both Add and Edit form page. 

I'm little bit confuse for which one is best concept single model class or seperate model class for better performace of project.