Bah, personally, I think we have an advantage on Pika, but that seems to be just my opinion. Yeah, a run away/campy Pika can be annoying, but once you learn how he moves, it's not too hard to intercept him. Just keep him running until he reaches an edge, then wall Bairs when he tries to get around you (usually with QAC, so stay close to platforms for a punish) or PS a jolt and run in and punish before the lag ends (only doable once you have him backed to a ledge.).
On the other hand, once you have his power, he's the one chasing after you, and the thing is, Pika cannot safely approach us, especially when we have his hat.
We also spam like 1800000 times better than he does, and it refreshes our Bair, which is a BIG problem for Pika. Both of us can combo each other about as well.
We can also punish a whiffed Thunder with both inhale and hammer (both versions), as well as cutter but I don't know why you'd want to use that one.
After 100%, Pika's ledge options become extremely limited and very punishable if we have his hat too (and no, I'm not JUST saying that due to the hammer kill. Fsmash punishes 3/4 of his options in that situation, and Bair punishes the last one. If he takes the jolts, the situation resets.)
Pika does have some strengths, don't get me wrong, but I just feel Kirby is overall better in this MU.
The only times I have lost to Pikachus were because the player was vastly better than I was.