I am wanting to know if i should use 165 or 180 grain ammo in a 300 wsm for hunting both deer and elk in eastern Oregon, if it helps the elk will be spike only since i can only go second season.

A 180gr bullet would be a good choice for elk, i wouldn't go lighter than a 165gr bullet, reguardless of who's bullet it is.

check out those xp3 winchester 180gr 300wsm...

I use 180 in my 300 WSM Federal 180 grain Nosler Partitions or Accubonds

Either one is fine, use a quality bullet with controlled expansion of some sort. I like trophy bonded tip and Barnes Triple shock x bullet. But bullet placement is more important than anything so shoot what the gun likes I guess..

Put the bullet where it counts with that .300 i guarantee you its gonna fall. Or go a very short distance.

I like the federal 180gr. exterem shock ammo. Just make sure that your rifle likes the ammo you want to shoot. If the rifle doesnt like the ammo it wont be as accurate. Try them both and see which one your rifle shoots best then stick with it.

Mine likes the 165gr Ballistic Tips ... but go with the one your gun shoots most accurately, 'cause either weight will be fine

Personally I would shoot a good 165 grain bullet but to be perfectly honest the dead elk won't know the difference.

If you choose to use one of the all copper bullets (TSX, GMX, E-tip, etc...) I would go with a 150 grain.

Either will do the job. The 165's will shoot a bit flatter but nothing to get excited over.
Just pick out a well constructed bullet such as noslers , ttbc ,etc and go with what ever shoots the best out of your rifle. Personally I stick to either Federal premium or Hornady ammo for best results in my rifles but every gun likes specific load. When you find it by a few boxes from the same lot and you're set for awhile.