Wood will always defy empirical data. A tree, growing right next to another of the same species and likely the same batch of seed, will not be the same as far as density, grain and weight. Add to that tree growing in totally different places, different water source/light and you can see the problem just among the one species. Wood selection for guitars is an art form when it comes to acoustics. However for electrics it comes down to: appearance, weight, hardness and cost. Not necessarily in that order.