Drupal multisite configuration with a single database and redirection based on IP
If you are using IP2Local and purely redirecting to completely independent url that has a directly associated database (users, content, configurations) you don't really need domain access. You could keep all the data in the same database (save time on table maintenance) and separate them with prefix's.

You will need domain access if you are centrally sharing content, users and admin tasks as well as the database but need to open or restrict access based on the domain that the user is accessing through. If your users need to cross from site1 to site2 or access common content, this would be the way to go. Domain gives you more flexibility and scalability that option 1 but may require a little more work to set up.