It has been my observation that the better known "brand" ammunition such as Winchester, Federal, etc. will display better accuracy through tighter groups.
That being said, it is the consistancy of the cartridges, rather than one round delivering better acuracy than one round from another batch.
Quality control is the key here. A man I know weighs each bullet, each powder charge, and separates his cases into lots as he loads. He, or course, shoots bench rest.