The Rec 7 is awesome. Skip the DI, Barrett just offered it as a slightly cheaper alternative, but the piston was always the flagship of the rifles.
Barrett does not have a bad rifle in their lineup. I have a few of their offerings and I can’t say enough good things about them. I’ve been considering an MRAD for years but always get stuck on there being no left hand option.
FWIW, all the 6ARC they shipped to the DoD are DI. DI and pistons are apples and oranges, there is no one "best" for every use case, they both have tradeoffs. I've moved from piston systems to DI, because I'd rather clean a little more often and have the recoil impulse/front weight balance I prefer, especially already tacking on suppressors and so forth.