I raised this question a few months ago; I had run across a negative comment about them, after I had bought a carton. The consensus of those with experience with the "new" primers was that there's no real difference.
The white-box primers said "For Regular or Magnum" or some such; the blue-box primers are separately for "Regular" or for "Magnum" IIRC. Maybe blue-box "Magnum" primers might be a tad hotter--or it might be some liability issue. I dunno.
I do know that for 50 years I have read the caution that just changing lot numbers in any of your components should mean dropping back 5% and working back up to max.
You can search the TFL archives for more info.