I'ed still rather have the larger round/rifle in those scenario. I'ed rather have it and not need it then the reverse, I don't think the downsides are significant enough to warrant the smaller caliber rifle. Again too, the ability to pickout a target at distance is going to keep you alive better or punch through tree they are hiding behind. I have two major problems with the new intermediate-intermediate rounds like the 6.8 Remington and 6.5 Grendel. The first is adoption, both rounds were designed for police and military use and last I paid attention neither had really gotten much attention from either fields. That might be a cultural problem with using a unfamiliar round or an issue of logistics of all new rifles or whatever. I suspect the pivot to the civilian market happened because the rounds advantages just aren't significant enough to switch to over either the 5.56 or 7.62 in each's intended roles for professional armed forces at least. It reminds me of the debate of a .40 S&W over a 9mm or .45ACP, want more rounds and less recoil use a 9mm or want heavier rounds use a .45 why would you ever take the .40 middle ground there with significantly heavier recoil then a 9mm but fewer rounds. The second is availability, these rounds have been on the market for a while now and they still aren't very common. I don't think scrounging around is going to net you a ton of 6.5 or 6.8 partially due to the aforementioned issues. I know that finding 5.56x45 or 7.62x51 wouldn't be difficult due to military adoption and civilian popularity and the same can be said for 7.62x39, 5.45x39 or 7.62x54 at least on the civilian side. This is only tangentially related but I always thought it would be a fun idea to have the British adopt the 6.5 balistics equivalent in the Fallout universe with the British .280 developed in the 50s. That coupled with the EM1 would make a fantastic fallout-ish gun, either something adopted by the European Commonwealth or like a post EC breakup emergency production kinda thing. The gun looks very fallout too, check it out.