IMHO...
I don't know for .308 DPMS... Never shot one but read alot. I'm not saying they aren't good rifles, because if they were, they wouldn't be in business, but there's the old saying: you get what you pay for. There must be good reasons why the AR10 is more expensive than the DPMS.
For what it worth, here's a quote from Tactical Small Arms of the 21st Century (2006) by Charles Cutshaw, about the AR10(T) : "Although the AR10(T) has not been formally adopted by the United States military, many special forces individuals have purchased AR10(T) rifles for operational use, preferring it to standard-issue weapons."
As for the SR25, here's a quote from the Illustrated Manual of Sniper Skills by Mark Sipcer: "The SR25 is considered by all users to be very accurate, but some have expressed reservations about its reliability in action.".
All I'm saying is that amongst great rifles, some seem to be "greater" than others.