Well basically what I feel that makes HRP unique compared to most other RP servers is how easy it is to jump right in and play. Most servers I have played are really hard to get into unless you have a friend who introduces you to it. HRP is pretty basic as you can view the full list of the rules in game and they are well defined, then the jobs are simple yet allow for countless RP situations that result in different experiences every time you play.
The things is, though, that I don't know of my post-apocalyptic lite RP servers; lots of serious ones like Fallout and Metro RP, but no lite variants. We may have something unique should we choose to pursue this.