Simple or Complex?

I am currently experiencing a conundrum with regard to Statistics representation. For the uninitiated, "Statistics" refers to the traits that make up one's character in an RPG. Things like physical strength, manual dexterity, street smarts, knowledge and perception are the usual fare when it comes to character composition. For Prototype, I have the following stats.

Strength: raw physical power.
Nastics: physical dexterity; how quickly and gracefully one moves.
Perception: powers of observation, hand-eye coordination.
Intelligence: book smarts.
Smarts: street smarts, charisma.
Looks: physical attractiveness.
Guts: physical endurance, how many punches you can take before you buckle.
Minerals: mental endurance.
Luck: how much the forces of the cosmos favor you.

These Statistics are rated from 1 to around 40 (can be higher depending on race, but that's not an issue at present). In order to reflect one's superior Statistics, high stats get a bonus to die rolls while low stats get a negative roll. Ratings of 10 and 11 are considered average and confer no bonus. Penalties start at 9, with a -1, and go down 1 point per rating. So, 8=-2, 7=-3 and so on. The catch is that low Stats will go up quickly, since it's easier to get from "Lousy" to "Average" than is to get from "Average" to "Superhuman". Ratings of 12 and up confer a +1 bonus every 4 levels, so Stats of 12 confer a +1, 16 gives a +2, 20 a +3, etc.

The only exception is Luck. Luck begins at 1, which =+1 for Luck and only Luck. Each rating of Luck confers that bonus. 2=+2, 3=+3, -5=-5. The question which is running through my mind at the moment is whether or not all Stats should act as Luck does, for the sake of simplicity, or whether I should leave it as is.

On the one hand, I like the idea of having a more expanded rating system, as it allows for more of a grey area. A simplified system would probably only have ratings ranging from -8 to 8.

There are many successful games which capitalize on both schools. Heavy Gear has a very simple system while other games like World of Warcraft utilize complex formula to calculate Statistics. While I dont wish to get as complicated as that (it makes little sense to me how exactly a bonus of "+25 Defense" does not actually increase your "Defense" stat by 25, but I'm sure they have a method to the madness somewhere) I do feel that it adds a certain depth to things.

Decisions, decisions.