Talk:Orianna/@comment-43887974-20191201045405/@comment-26808509-20200131125711

It depends. Both items give you very different and situational things so there can't be made a general statement.

What you need to understand is that flat penetration is a purely early game oriented stat. The MR per level on most champions is enough that you no longer deal true damage to them in the late game with double pen. That's why you should allways only buy Oblivion Orb if you want the early powerspike and then leave it there to buy other important items. Upgrading Oblivion Orb is only worth if you need to counter healing. Other than that, you should NEVER upgrade it. Especially not early on. Oblivion Orb + a Needlesly Large Rod is about the same price as a fully upgraded Morello (even 150 gold less), it gives you 5 more AP and brings you closer to your Rabadons.

So that means, you only go Oblivion Orb (and not upgrade it!) if you play against low MR targets (a team full of squishies or you being the only magic dmg threat which will reduce the probability of your enemies buying early MR). If they don't have healing champs, you can sell it in the late game for a different item, as the flat pen will be quite useless at that point (especially since you should have Void then). If they DO have healing champs, it's the only situation when you should ever upgrade it. Other then that, only Obilivion Orb and selling it later on.

Liandrys on the other hand is good against tanky and MR heavy teams, obviously. And this one you will upgrade immediately. And follow up with a Void Staff to compensate your lack of penetration.