I know another barrel question. M24 or 3B

Looking to build a 6.5CM shooting rig for bench currently or PRS down the road. I have the option between 2 barrels, 24inch barrel. Both options are a Bartlein M24 and 3B fluted both from Stuteville. I'm looking at a MPA matrix or pro II chassis, I want to shoot out to 1200 yards at some point and run a can as well. Maybe 6-8 round string at a time. Weights not a concern just want to make sure I go the right route for the barrel.

After doing some reading on previous post I see M24 mentioned a lot, but still lost on some information between the two. Looking for advice.