Re: POWDER.IS IT A PERSONAL PREFERANCE?
In answer to the title of your post, it really shouldn't boil down to personal preference. First of all, there are powders that are too fast or too slow for a .308. Secondly, consider the range of conditions you will use it in. The less temperature sensitivity the better. Third, some powder(s) will be more accurate with your combination of brass, primer, bullet and seating depth.
Two that I've had good luck with in both a 20" and a 24" barrel are Varget and RL-15, both with 165-168 gr. projectiles. But others listed above are worth trying. I made the mistake of buying 4 lbs. of IMR 3031 back when I first started, not realizing it was only good for 147-150 gr. bullets out of my rifles. I use it but only for plinking loads with a hodgepodge of once-fired brass. Nowadays, I load for both rifles with Varget. Fortunately, both rifles really like the same exact load. All I have to do is keep the brass carefully sorted for each rifle.
If you end up liking a powder, either buy an 8 lb. jug of it or get 7-8 lbs. of the same lot. A powder like Varget is pretty temperature insensitive, but will vary slightly from lot to lot. You might find yourself adjusting a load .2-.4 grains just to get back to the same sweet spot.