It's sounds like your biggest concern is tread wear and you'll typically get about 30% more wear out of the all-season tires than summer tires. The tires you were comparing consisted of 2 summer tires and 1 all-season. I think as far as value, performance and tread life you would be most happy with the Continental Extreme Contact DWS. As far as fitting the 265's I'm not sure, maybe someone on the forum with a GS can let you know if they have used this size before.
Continental Extreme Contact DWS