From the Persona Management Deployment Guide, Page 3:
"Advantages of View Persona Management
Before the advent of View Persona Management, View administrators handled user profiles by:
• Implementing Windows roaming profiles
• Using third-party virtual profile managers
• Keeping the user profile local by using a dedicated pool of persistent desktops, or persistent disks attached
to nonpersistent desktops
Traditional roaming profiles have serious performance issues when a large number of users log in or log out
simultaneously. In addition, managing user profiles through Windows Active Directory may have repercussions
for more users than intended.
Choosing to implement a dedicated pool of persistent desktops, or persistent attached disks, is not optimal
because of the storage space required for individual desktops or disks.
VMware includes in View 5 an integrated virtual profile management system that is easy to set up, minimizes
login and logout time, and allows for flexibility in choosing desktop pool types."
Also, only the settings/files that are needed are loaded during login which makes the login process a lot quicker.
Hope that helps a bit.