I only own one SBR...but this is my favorite upper (6.5" 22LR):
I also have a 12.5" 6.8 SPC upper for it but I'm not too thrilled with that caliber.
It's accurate enough but bullet selection isn't great - there are plenty available but not too many that are good for hunting. Either they're thin skinned varmint bullets like the V Max or heavier constructed bullets that don't open up well at the 6.8's velocities. Barnes makes an all copper bullet that's supposed to work great for hunting but my gun doesn't shoot that bullet well. Brass and bullets cost more so it's not a good plinker like a 5.56. Mags are scarce, too. If I was starting from scratch again I would go with a 300 BLK instead. As it is I'm thinking of selling the 6.8 upper and buying an AR10, and then eventually building a 10.5" 5.56 upper for a fun blasting toy.