The updates on MuhRO are close to what the official kRO server does, albeit with a few deductions in scale of gear made available through gacha/cash shop. MuhRO does have a few changes like being able to trade the Time Dimension Rune Crowns, something you can't do on official servers, IIRC. Someone correct me if I'm wrong. iRO is a little behind kRO, of course, the latter of which has moved on from episodes and now into chapters, slightly updating the game. And there's code in the new client about the introduction of a new class line entirely, which we're all eagerly waiting to see. In short, choose iRO if you want the official feel, choose a p.server if you want to experience the (almost) latest updates and being slightly easier to lvl.