How many grains per pound do YOU feel is best for hunting?
If the arrow weight calculators (such as the one at bowjackson.com) are correct, my arrows are 437gr. My bow is currently set to 65# so I'm getting about 6.72gr per pound. Seems reasonable to me although I might lower the poundage some just to please my shoulder. At 60# it would be 7.28gr per pound.
I shoot 70lbs with 6grains per lb. I hardly ever dont get pass through arrow. Remember accurate arrow placement is the key. You should be alright with either set up.
Personally, I don't think there is a "BEST" grn/lb spec for hunting. Just get your spine right, and tune your bow. I would say anything from 5-15 grains/pound can work just fine. There is no BEST.