RE: Best Round for 308 Winchester
A 168 gr mathc hollow point is NOT a good hunting bullet. even though its a hollow point, it has a thicker jacket and will not expand much, in fact it will behave more like a FMJ bullet. This is the reason why you got an exit wound the same size as the bullet diameter. While a well placed shot will do the job well, it is not meant to be a hunting bullet and shouldn't be used as one.
My preference is 165 gr BTSP nosler partitions- these will give excellent expansion and weight retention combined with a high ballistic coefficient for making longer shots. I have taken several deer with this bullet with good results. This year I switched to Hornady 165 gr btsp interlocks, they shoot accurately but unfortunately I didn't get a deer this last season to report on their performance. Both bullets I load with 41.0 gr of 4064.
On a further note, I have used 150 gr. remington corelokts for plinking in the past. They gave decent accuracy, and I've never heard stories of corelokts giving bad performance on game.