Every percentile system I can think of rolls low, so don't sweat it.
Originally Posted by templeorder
Rolling high does have a few slight advantages over rolling low:
- Adding or comparing numbers is a little faster than subtracting them, especially for the mathematically challenged. Penalties subtract from the die total in roll-low, whereas a penalty in roll high might add to the "target number" or opposing roll.
- The GM can withhold the "target number" until the player rolls, allowing for more surprise. Theoretically, he could also ask players to give him a "margin of success" and then declare whether the action worked or not, but that's not quite as natural.
- Once skills/attributes/whatever go over 100%, either progress stops or the rules must define what "over 100%" means. (In GURPS, skills over 20 face a similar problem: are there enough skill penalties that a 21 is more useful than 20?) By contrast, roll-over scales up naturally ... although at high enough skill levels the dice rolls become almost superfluous.
Mathematically, there's no difference, and the relative advantages I listed above are debatable. (At least one thread here debated them.) Really, it depends on the assumptions and goals of the game's design. Do you want experts to "top out" at some point, or can they go "beyond the impossible"? How common are penalties to the die roll? (If every conflict is roll vs. roll, the game may not have skill penalties at all.) What about bonuses to the die roll? Are listening at a door or sneaking past a guard skill contests, straight rolls, or something else?
"On two occasions I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question."
- Charles Babbage (1791 - 1871)