I did a quick google search and thought I would post a list of different features that the 2 Metioned anti-hack programs offer
Major Features in PunkBuster™
(some editions of PunkBuster™ do not have all of these features)
Real-time scanning of memory by PB Client on players' computers searching for known hacks/cheats
Throttled two-tiered background auto-update system using multiple Internet Master Servers to provide end-user security ensuring that no false or corrupted updates can be installed on players' computers
Frequent status reports (highly encrypted) are sent to the PB Server by all players and the PB Server raises a violation when necessary which causes the offending player to be removed from the game and all other players are *******d of the violation
PB Admins can also manually remove players from the game for a specified number of minutes or permanently ban if desired
PB Servers can optionally be configured to randomly check player settings looking for known exploits of the game engine
PB Admins can request actual screenshot samples from specific players and/or can configure the PB Server to randomly grab screenshot samples from players during gameplay
An optional "bad name" facility is provided so that PB Admins can prevent players from using offensive player names containing unwanted profanity or racial slurs
Search functions are provided for PB Admins who wish to search player's keybindings and scripts for anything that may be known to exploit the game
The PunkBuster™ Player Power facility can be configured to allow players to self-administer game servers when the Server Administrator is not present entirely without the need for passwords
PB Servers have an optional built-in mini http web server interface that allows the game server to be remotely administered via a web browser from anywhere over the Internet
FEATURES of HackShield
Pro*
Memory Hacking Protection
Prevents memory excess of game hacking
Speed Hack Protection
Detects and blocks speed hack programs that tempers with system timer
Debugger Protection
Blocks hacker's debugging tools for auditing and analysis of code
Message Hook Protection
Makes message hooking function of game hacking tools useless and obsolete
Auto-mouse Protection
Blocks auto mouse operation, making it ineffective in games
File Change and Forgery Protection
Detects and blocks changes or forgery of files
Hacking tools and blocking detection
Detects hacking tools and terminates client game connection from server
Run-time Forgery Protection
Prevents from forging runtime modules of HackShield
Executable File Packing
Protects HackShield, hacking protection functions, itself from hacking
Network Packet Encryption
Encrypts network packet in NIST Rijndael AES format
Data File Encryption
Encrypts data files passed between client and server
Server-side Crack Protection
Regularly checks for changes or forges of executable file at client
Executable File Encryption
Encrypts game executables in real-time
Consistent and Continuous Update
Updates with new hacking tool pattern files and protection modules
Hope this can help settle the dispute or even further discussions
*Please Note: Punkbuster has alot more features then the ones mentioned above*