With the 165grn ABs I was able to get a little more accuracy with H4895, but had a Varget load that was about 1MOA, or slightly over, that was faster. I'd have to look at my notes to divulge many details, but the load I hunted with this year was H4895. It was shooting about 2625 fps and was sub MOA. The Varget load was good, certainly used factory ammo that was worse, but it was zipping about 2700.Both are “Extreme” extruded powders with minimal temp sensitivity. Varget has a reputation of being a little more consistent/precise. Very similar powder usage and very similar velocity. This is a coin toss. I typically would start with Varget unless I thought I might want to do reduce loads for a new shooter in which case I would start with H4895. But for 150 gn .308 Win I view them as nearly interchangeable.
Not necessarily a switch, just trying something different. Lighter, faster, flatter shooting. Hunting season ended a couple weeks ago, so now I'm just moving into the time when I experiment with stuff. That's all. I might never shoot it at an animal, but if I find something kick butt, I might.If you have 165's dialed in already, I see NO good justification to switch to a 150. Many moons ago I started with 150's and had a modicum level of success with them.