Luke Skywalker (The Ellimist) vs. Reborn Palpatine (DarthAnt66)
Here is the skeleton of my case:
1. DE Luke is already greater than nexus-amped Sidious as a duelist with just some help from Leia, who was "unlocking hidden reserves" or something. The several decades to his prime would presumably unlock more of that potential than what a rather sparsely trained Leia could do.
2. We know that Luke's potential is greater than Palpatine's, and it's very difficult to imagine that by, say, LotF, where he's in the same decade of age as RotS Sidious, he hasn't far surpassed him.
3. The above two points are especially true given that Luke has a learning curve essentially unseen in the mythos; by ESB he's described by Vader as the most powerful Jedi he's ever faced even though he's been training for like a month, and then after a few months he's able to match his father in sabers. By DE he's able to beat Palpatine with just a bit of a bump. And it seems like Luke's really massive leap forward hadn't happened until the New Jedi Order.
4. Lucas pretty much confirms that Luke eventually fulfills his father's potential. Even if you don't take Lucas's judgment on such things literally, the holistic intent of Luke having that potential is clear, and there's no reason why after decades of growth he never reaches it.
5. In terms of feats, Luke's outstrip Palpatine's when you compare them side by side, .i.e. his telekinesis feats are superior (black holes), as are his illusion feats, etc.
Potential counter-points:
"Palpatine's Force storms" - not a fair comparison given that Luke obviously wouldn't use them.
"Luke's struggles against mundane foes" - it's been confirmed on many occasions that Luke rarely ever goes all-out. In Specter of the Past or something he notes that he shouldn't go all-out on some pirates, in LotF Jaina acknowledges that she doesn't know more than a fraction of Luke's power despite having been with him in TUF and in many other contests, etc. But he'd go all-out on Palpatine.