AR in 6.5 Grendel

My wife just realized the fun of my rock river AR-15 in 5.56 and decided its hers and told me to buy a new one. Who am I to fight with that! I have been Kicking around Either going to a 6.5 Grendel or Ar-10 in .308.....Pros/cons of the Grendel? I figured on buying another 5.56 upper for the new rifle also for paper/Plinking on the cheap and easier to get ammo. I would be reloading for the 6.5 or .308 once I get the rest of my equipment...