Those are brands. Each brand will make forks of different quality levels, so you really need to know the specific model. For example, I'd take an RST Space Jump over a RockShox Dart any day, but a RockShox Lyrik will kick the crap out of an RST Launch. Most of the time, the Suntours and RSTs that get put on entry level bikes are crap, though RockShox Darts really aren't that much better (if they're even better at all).