Binoculars, hands down. IMO, spotting scopes require too much hardware to be effective in the field for hunting purposes.
I'd probably want 20x ... but that's a personal choice.
Best bet is to stop by your local dealer, pick out an object about the size of the game you're hunting at 500 yards and take a look with something he has in stock. You'll know very quickly which suits you best.
And ..... expect to pay a hefty price for a good pair of binos. I'd expect to pay $600 to $800 (maybe a bit more) for a pair suitable for hunting. The glas is everything. If it's got good glass you can be pretty sure it's got good mechanics.
I carry Bushnell 10 X 42 ARC 1 Mile laser range finding binos and love them. Yeah, the glass is noe Swarovski but neither is the price. Plus I get far better laser ranging performance than my friend's pricier Ziess LRF binoculars.