Brother Bob, that's a great question.
I maintain that I prefer not to be shot by anything.
It doesn't seem like there would be a lot of difference between a 140 to 143 gr tipped or bonded 6.5 projectile and a 168 to 175 gr tipped or bonded 308 for duty use, and I'm willing to concede there may not be.
The trouble is as of right now there is no compelling proof that the 6.5 could fill that role.
At some point Gary or the Chesapeake guys may have that answer, and I'm sure they will. For now, no.
308 is such a documented predictable performer it would be unacceptable to change to a "flavor of the month" cartridge, even a great one like 6.5 or 260.
I do not personally know of any agency that does not use 308 as their primary sniper cartridge, with an addition of coverage for Heavy Target Interdiction where some use 338 and more and more are going to 50 after the Dallas experience.
To make a long answer longer....
The 308 performance against intermediate barriers is good. I'm looking at the 143 ELD-X as a potential duty round and I bet Gary is or will at some point, just for the data. I think it may do the job. But would it outperform the 308 in a way that would make us look at replacing the 308 and a 168 Amax or similar? I'll go out on a limb with no objective evidence yet and say no way.
I currently have four 6.5's in the house, and during a course most guys end up shooting them (and others), especially at night because all my guns are set up for CNVD and a lot of guys' duty guns don't and that's what they are coming to get exposed to. Everyone LOVES shooting a 6.5. The Hornady factory stuff is plentiful, relatively cheap, and match quality ammo. It gives you a solid 6 mph wind bracket to work with so is a lot like a 300 WM for wind formulas, but you can shoot it all day and night. It is FUN.
My completely un-scientific, non-meaningful, completely biased hesitation comes when at 800 yards you hear and see the difference produced in the steel between that 6.5 and 308. With the 6.5 it is a barely perceptible "ting" and a small mark on the paint versus a "clang" and a big, easily seen splat on the white with 308. Every. Time.
There is a clue in there somewhere.
When we think about barriers, peer-engagements against opponents in ballistic armor, etc., I need a lot more info before I could ever tell a guy they should consider adding a 6.5 to their work line-up.
For myself, the confidence I have behind the 308 based on a long track record in the field and in the lab coupled with premium projectiles and the right platform gives me a combo I do not have any anxiety about being capable of performing on demand.