security/management concern: external database users vs roles management

Hi,

I'm new in drupal world and I have project where I should create a new registration form for a specific type of users. I need to make a quick decision about whether
1-I'll create new database for those users account, so separate user management mecanism from drupal users one
2-add those users to drupal users table and manage roles/permissions.

Which solution is safer/the best?

Thanks