Depends on goals. Neither of your options is really ideal. Any "real" long range rifle, with optimized ballistics, will have a relatively short barrel life. To get long barrel life you have to make fairly drastic compromises on the ballistics. I have a 308 and a 223. For me they are both training rifles. Components are more readily available, and cheaper than 6.5mm 7mm or 338 calibers. If you can shoot your 308 well, then you should not need a ton of time on a more capable rifle. Actual hunts will burn through very little ammo, so a hunting rifle will last a long time. But blasting at prairie dogs or competition is a different story...

In addition, if you go with a factory rifle, you have to be sure you get a decent barrel and also barrel twist rate. In my experience, factory barrels are hit and miss and in some chamberings, never offer a suitable twist for high BC bullets and might not be throated right either. So be aware that your factory rig may not work out too well for you. So far I do not have any factory barrels left on any of my rigs. My suggestion is to buy a used rifle at a discount and plan on screwing a custom barrel onto it from the start. Just get everything else you want (action, stock, magazine)...