Rank these universities (undergrad) prestige and reputation for employer reputation?

Why? These always lead to shit storms.

I would guess Columbia (at least for the U.S.), but it depends whether UPenn means Wharton (or if you'd intend to transfer in once accepted).

UPenn... Wharton or not is better than anything.

RANKINGS!!!

PRESTIGE!!!

Just so you know this board generally hates questions like this, but here is my opinion (the fact that this is an opinionated answer cannot be stressed enough)

For worldwide: LSE Columbia Upenn Imperial

For US: Columbia (just because being in NYC and OCR, as well as being able to do part-time internships) LSE/UPenn (again only for OCR) Imperial

UK: LSE Imperial Columbia Upenn

First off, who cares about "WORLDWIDE" reputation? Schools like UTexas prove that only regional reputation matters. Who gives a fuck about "prestige"? The only thing that matters is quality of OCR and alumni network.

For US: Wharton>Columbia>Upenn-CAS>LSE>Imperial.

EDIT: Just read your other post, and saw that you're a 2nd year at Oxford. You should just get a job at an American BB's London office, and then do an internal transfer. If you can't or don't want to wait that long, then go for MSF programs from MIT/Princeton.