I'm another one in the "buy it with the walnut, then purchase a synth beater stock for the sloppy or rough days"
for range use or "just having", to my mind wood is what belongs on M1A/M-14 style rifles. and for regular range use or match types where there isn't a high likelihood of the rifle getting "beat up" i'd keep it in wood
that said, if i had, for whatever reason, wanted to hunt with an M1A, or use it in a 3-gun match, or somewhere else where the odds of it being battered around were fairly high, or if it's simply a wet, miserable, nasty day. I'd have it in a synth stock. probably one of the old brown GI fiberglass ones.