I concur with Longrifle. Synthetic stocks are, ultimately, more stable. But, I would add a recommendation for laminated stocks. I don't know how you feel about the appearance of them, (some people absolutely hate them)...but, properly sealed, they are virtually as stable as synthetics...with the feel of wood. I prefer them, above all others.

The downside is - laminated stocks often are a bit heavier than synthetics. This doesn't bother me, though, as it simply helps reduce felt recoil. But, it is something to be considered.