This is hilarious. In other words, Schumer would oppose appointing someone as FBI director, even though he'd support the exact same person as a special prosecutor.
It reveals their entire purpose with this investigation -- it is not to resolve or complete it, but rather to drag it out for as long as possible.
Schumer knows that Trump himself isn't under investigation, and that once the investigation is resolved, he'll be cleared. And that's the absolute last thing Schumer and the rest of the 'Rats want. They want Trump to remain under a cloud for as long as possible.
So, they're pushing for a special prosecutor precisely because they know that would require a virtual restarting of the entire investigation into guys like Manafort and Flynn, and drag the whole thing out very possibly until the midterms. That is their entire goal in this, and Republicans who make noises about how the appointment of a special prosecutor would "help" Trump are missing the point entirely.
Comey was a disaster because any exoneration by him wouldn't have been worth squat. Trump needs to appoint someone to head the FBI whose integrity can't be impeached, and who won't be the type to drag it out unnecessarily.