You haul merits back and forth in solo, you run the risk of getting shot at by NPCs. You haul merits back and forth in open, you run the risk of getting shot at by NPCs and players. The risk is higher in Open, as Sandro told us, therefore your efficiency there is lower. Powerplay, as a competitive feature, is all about efficiency, so PP mostly happens in solo and groups, where the efficiency is highest and you can reach your goal fastest before the others. The modes are treated equally, but since there is an in-built handicap to one of them, the end result is that they aren't equal in practice, which is what Sandro would like to fix. That's equality, but that's certainly not equity.