What effects do system mechanics have on story?
When I started gaming, I was a big supporter of the d20 System. One system that could do potentially everything? A unified, easy-to-understand mechanic that just so happened to line up directly with the world's most popular roleplaying game? Sounds great, right?
Unfortunately, in practice, results were always sort of mediocre. While certain ports of the d20 System--notably Call of Cthulhu d20--managed to maintain atmosphere and tone, many other interpretations of the system (even by big publishers) were bloated, flavorless, and just 'meh'. d20 Apocalypse was like that for me: while the post-apocalyptic feel in gaming has always been ripe for great ideas, but the quintessential d20 post-apoc sourcebook left me unimpressed.
Over time, I came to realize a hard lesson: just because you can make something in a generic system doesn't mean that you should. Thanks to The Journeyman GM, I love Savage Worlds and its various settings, though truth be told, I can't see myself ever running a true horror game in SW. Savage Worlds was built to emulate a pulpy, adventuresome feel, with Bennies and streamlined damage that allow for quick recovery. In a horror game? You don't want either of those things. And, while Deadlands certainly contains aspects of horror, it's hard to truly be "scared" when you're playing a hard-bitten gunslinger, a mad scientist, or Gambit from the X-Men.
|The right tool for the right job.|
Think of game mechanics in terms of a tool box. If you were going to hang a picture, you'd use a hammer and a nail. You might instead use a drill and screws. However, you probably wouldn't decide to use a wrench and spackle, even though they might possibly be able to hold the picture up. The same thing goes for game mechanics.
|This guy just lost some SAN points...|
The best games use their mechanics to support their theme. Call of Cthulhu encourages diverse skill use by tying advancement to using skills throughout the game. CoC emphasizes the descent into madness through its ubiquitous "sanity spiral" wherein failing Sanity tests not only can drive you crazy now, but also makes you more likely to fail further Sanity tests. Cold Steel Wardens emphasizes brutal combat and psychologically damaged heroes, spending an entire chapter (in a nominally superheroic game) detailing Injuries and Psychoses. Dresden Files uses Aspects and very broad skills to emulate the flexibility of its arcanely-powered characters.
In the end, you've got to use the best tool for the job. And, while something like d20 or GURPS or d% might be able to do the job, why not choose a more specialized tool that makes your job easier? In this brave new world of digital publishing, there are games to emulate nearly every genre imaginable: don't be afraid to give something new a try!