Zappo
Explorer
Rolling results in slightly higher scores than 25 PB. However, PB allows you to min/max more effectively. So, I think that 25 PB is roughly correct. I don't know if this is common, but lots of DMs I've met that argue that rolling is better than 25 PB tend to let the player choose between two or three sets, or reroll one stat, or something similar. PB is only equivalent if you play the rolling method by the book, of course.