Hi Scotty
AS you've had some exposure it really comes down to what you are more interested in.
In terms of security, is it more than roles and users. However, the system & integration side of security (e.g. securing RFCs, trusted systems, SSO or other authentication) might still sit with the System Administrator.
At the same time if you keep to users and roles as your definition for security then this is a good career path if you like to understand business process, segregation of duties, etc. In a way this area of security is more functional related.
I chose security background (never did Basis) as I like learning a little about a lot (all the different modules, components, etc). Security continually comes up in top 5 priorities and issues - particularly as we move toward cloud environments.
With Basis/System admin, as companies move the cloud and simplify landscapes there might be more competition. Also, a lot of this work can be out of hours (system refreshes and backups, etc) so if you don't think graveyard shifts it might not be suited to you. This would really depend on your emploer
But with Basis, if you enjoy the more technical side - installations, databases, transport management then this is a good pick
If you like transport management, you could look at continuing down Basis Path and look at specialising in Solution Manager Component. Within here there is a module CHaRM for change request management.
In short, you've had enough exposure to this world and really the choice should come down to what you enjoy and are good at. Until you decide, keep trying to get as much exposure to system administration activities and security (e.g. system performance monitoring, applying SAP Notes, security log monitoring, GRC or Idm if you company uses it, client refreshes).
Regards
Colleen