The main difference between the personal and licensed versions is the inclusion of Ad-Watch, which is a realtime monitor for your system.

See Ad-Watch Defined.

Here is a quick look at the differences between our new offerings.
Note: all versions include the options of the version(s) preceeding it.

Ad-Aware SE Personal:

CSI (Code Sequence Identification) Technology
Links to more information on detected content from our website
Extended protection against DLL-injection
New safety option that allows you to write protect sensitive system files such as the Hosts file
New comprehensive help manual
Configurations protection and hardened against third party uninstall
Enhanced Data base
Personal version plug-ins and extensions
Full featured quarantine support
Tweaks (optional configurations) (Limited)
Browser hijack protection
Customizable scanning (Limited)
Improved safety and redundant backups
Improved logging capability

Ad-Aware SE Plus:

Tweaks (optional configurations)
Customizable scanning
Automated Definitions file update support
Automated and silent operation for Ad-Aware and Ad-Watch
Basic command line parameters
Automated scanning
Automated Blocking
Plus version plug-ins and extensions
Ad-watch real-time monitor
Registry protection
Executable file extension protection
Free E-mail support
Advanced filtering
Printable reports
Ad-Watch rule editor
Popup Blocking (Internet Explorer only) Sites manager included in Ad-Watch

Ad-Aware SE Professional:

Process manager/viewer*
Additional command line parameters
Additional menu and export options for reports
Professional only plug-ins and extensions
Mapped network, UNC, and ram drive support

*With the Professional edition, we have included a powerful Process
manager/viewer that offers more than an ordinary process monitor. It has
been designed to completely support our all-new Plug-in interface and the
exporting features that are only available with the Plus and Professional
Editions.

What's new in Ad-Aware SE Professional edition?

Scanning engine improvements
Extended Memory scanning
Now scans all modules loaded by a process
uses our all new CSI (Code Sequence Identification) technology to identify
new and unknown variants of known targets
Extended protection against DLL-injection, SE can unload process modules on
the fly

Extended Registry scanning
Now scans registry branches of multiple user accounts
Performs additional smart checks to detect dynamically created references
Scanning speed noticeably faster
Extended Scanning for known and unknown/possible Browser-Hijackers

Extended Disk scanning
Now scans and lists alternate Data-streams on NTFS volumes
Now Ad-Aware supports scanning of Cabinet files, (including spanned
archives)
Scanning speed increased
Improved Hosts-file scan
Now Ad-Aware and Ad-Watch Use much smaller reference files

Several User Interface improvements
Improved Graphical UI
Ad-Aware now supports custom graphical Skins
more user friendly Plug-in/Extension GUI (Plug-ins and Extensions now shown
on separate screens)
New Scan Result view, Includes a scan summary and Detailed view
Ad-Aware now linked to the online TAC database

Multiple New Tweak options
Unloading of process modules during a scan
Obtaining command line of scanned processes
Ignoring spanned cab files
Scan registry for all users instead of current user only
Permanent archive caching
Always try to unload modules before deletion
Disable manual quarantine if auto quarantine is selected
Block pop-ups aggressively
Load aw minimized
Hide Ad-watch tray icon
Write protect system files after repair
Limit drive selection to fixed drives
Use gridlines in item lists
Log file detail section condensed

Proc-watch
Improved ProcWatch scanning capabilities and scanning speed (Using the new
fingerprint engine)
Several ProcWatch Interface improvements
Option to create a Hexdump of the process memory or dump the process memory
to disk

Several Log file improvements
Includes support for separate removal-Log files
Allows adding a Reference summary/index to log files
Log file contains overall more detailed information

Ad-watch
Several GUI improvements
Ad-watch now supports Cookie Blocking
Site-manager to edit the popup-blacklist included
Ad-watch now uses the new CSI technology to detect new and unknown variants
of known targets
New Ad-watch configuration screen
New rules editor for pre-defined blocking exclusions
Support for hiding the Ad-Watch tray icon for unattended operation