I know some people who use the boss attachment while at the range,for the big caliber shoulder pounders,and then when hunting change to the conventional recoil attachment.They have not found there to be significant accuracy difference's and they accomplish what they want to accomplish.
As previously stated I have a .270 a-bolt that came with both attachments,I wasn't concerned about recoil so I have never shot my rifle with the boss on it only the CR.I don't as of yet hand load and was frustrated by the out of the box accuracy I was experiencing with other rifles,so the ability to use a bullet that I wished to and adjust the gun to the bullet instead of the other way around appealed to me.It still does!