I don't have anywhere near the experience that Danny does but have noticed that any wood which goes from wet to dry with minimal warping will tend to stay straight during minor moisture changes. Also any piece that warps a lot when drying is much more likely to warp again when machined. Limbs are a good example; they warp from stress while drying and will warp again every time they are machined. Nice straight trees make straight lumber, crooked trees make crooked lumber regardless of the variety.