When comparing Quake III Arena vs Garry's Mod, the Slant community recommends Garry's Mod for most people. In the question“What are the best LAN party PC games?” Garry's Mod is ranked 17th while Quake III Arena is ranked 25th. The most important reason people chose Garry's Mod is:
Garry's Mod has a wide variety of [community made add-ons](http://steamcommunity.com/workshop/browse/?appid=4000), which deeply extends the games content and versatility. Pretty much, if you can think of it, someone has probably already made it.
Ranked in these QuestionsQuestion Ranking
Pro Worthwhile time investment for competitive play
Not many available FPS games have such a high skill ceiling as Quake III Arena, making this a great game to invest time into, for those that want to get to a competitive level.
Pro Plenty of variation with multiple game modes keeps the gameplay fresh
Deathmatch, Team Deathmatch and Capture the Flag are the various modes that players can select within the game. This allows for enough change in gameplay for the user so that the game never gets old too fast.
Pro You can easily run the game on low end PC's
Due to the age of the title (released 1999) and the requirements of said title in the modern day, the game can easily be played on just about any PC from the last 10 years.
Pro Offline LAN support
By using a LAN connection, multiple computers can facilitate multiplayer without the need for an internet connection.
Pro Tons of community made add-ons allows the game to continually grow
Garry's Mod has a wide variety of community made add-ons, which deeply extends the games content and versatility. Pretty much, if you can think of it, someone has probably already made it.
Pro The games mechanics and mods allow for ridiculously funny gameplay
You can do some really crazy things in this game thanks to all of the community mods available as well as the built in, in game tools. Pretty much any scenario can play out in the game, if you so desire. Of course the winning combination of funny tends to be when players are just goofing around.
Con Poor quality voice-overs
Given that it is an older title and thus released when studios put little money towards quality voice-overs, Quake III Arena stands out as one of the worst of its kind, not least on account of the game announcer who is one of the main culprits.
Con Previously free to download
Garry's Mod used to be a free download but it is now a paid game on the Steam store.
Con Tons of bugs
At least in earlier versions.