Look at the available bullets in .284 vs. .277 and you will have your answer. Hint. Thank me later. (Sorry, I couldn't help myself)
this came up a few years ago and I remember doing the research and found only a couple more bullets available in 284 as compared to 277 between 120 and 160 grs.
It may be somewhat different today but if someone wants to do the research I think you'd be surprised.