I think the 6.5 prc is more comfortable to shoot and should take down just about anything with proper shot placement. 7 prc kicks like a mule. Plus ammo availability and cost is significantly better for 6.5 prc
I do love my 6.5 Grendel in the AR-15 platform. Can’t beat the cartridge for an AR-15. Definitely better options with AR-10 platform or bolt rifles but heavier guns.