The only thing a buffer adds is weight and, therefore, inertia. It passively absorbs recoil at the cost of adding additional weight to your rifle. A brake, on the other hand, actively reduces recoil by redirecting gasses and providing straight-line pull force to the muzzle. This also allows it to be fine-tuned to prevent twisting or other motions induced by the rifle's function. A brake will always be inherently superior to any passive recoil buffer.
A .223 rifle can sometimes have a slightly sharp recoil. That is something I have also noticed even with my Saiga .223 which is far from lightweight. It's not a heavy recoil, but it is sharp. That can be uncomfortable for some shooters. A brake will definitely help with this. Increasing the weight of the bullets used will also help.