Top BB (ie GS, MS) v Top MM (ie HW, Jeff etc) v Boutiques

The quality of any opportunity at the lower execution level depends on one thing: deal flow. If you do lots of deals you'll have a good experience and you'll have lots to talk about in an interview. At a BB you'll work on some of the biggest and most complicated deals, but then again you're in a fairly large organization that may want you to do the same type of thing over and over and over again and your experience may suffer as a result. At a MM you'll work on smaller deals but since the fees are smaller they have to do a slightly bigger volume of deals to make money and that may not be realistic in this market. Thus you might be pitching a lot rather than working on live deals leaving you with less to discuss in interviews. There is literally no way to predict who will be getting deal flow. So your best bet is to go with stable market players, whether they are BB or MM, and hopefully the deals will be there.

None of this has anything to do with "prestige," which may be the single most psychologically damaging concept to inflict on young, eager, stupid ears. Think about it, the whole idea of "prestige" assumes there is someone above you who will be sufficiently impressed at your awesome self. So embedded in the very concept is the idea that you are still second rate. Even if there is no one actually better then you, even if you are literally the best person in the world, pursuing prestige will simply cause you to look for / invent / convince yourself that there ARE people out there that you still need to impress. A pathetic and ridiculous state of mind if you ask me. Rid yourself of this nonsense and ask yourself what you want to do? Then do that.