While I really like my MWS and would place it at the top of 308 guns, I really don't think there is a best, just what works best for the user. While it is used down range by groups that walk around quite a bit, I am not sure that I would recommend it for walkabout/hunting rifle as there are just better 308 gas guns for that role.
I have owned, a built up armalite, a built up mega with noveske barrel, I Currently own a MWS, SR25 and Scar 17. I find the MWS a little more appealing that my other current rifles as its just more flexible than the other two. While the MWS might be a little heavier that KAC or FN, my ability to go from a 13.5 308 barrel to a 20 inch 6.5 barrel in under two minutes is pretty nice.
At the end of the day there are a lot of good 308 gas guns out there, I personally am a really big fan of KAC and LMT. I also really like the idea of a GAP accuracy build