How do I know if I'm using the Cisco AnyConnect VPN or the Prisma Access VPN?

There are many differences. The easiest way to tell is by the name of the app you're using, but there are also differences in settings/look feel.

The Cisco Anyconnect VPN

• The app it uses is called Cisco Anyconnect Secure Mobility Client
• You connect to vpn.mit.edu/duo.
• The login screen once you start your Cisco Anyconnect Secure Mobility Client
  app looks like:
  

Prisma Access VPN

• The app it uses is called GlobalProtect.
• You connect to mit.gpcloudservice.com
• You have a globe icon in your menu/task bar that lets you connect/disconnect.
• On the desktop, you connect by clicking on the globe icon and pressing Connect.
  
• On mobile devices, you connect and disconnect by tapping the shield in the GlobalProtect app.