hmm yeah not sure about the comment about exit opps in the BO or MO of a bulge bracket.. doesnt really seem to make sense.. i think traders who have that experience did so as a stepping stone to becoming a trader when starting out their careers as so many traders do - but if you start out your career trading you dont stop and do support functions for a while.. if you're a trader now you don't want to go to the BO/MO and then try to get back to the FO.. sounds dizzying and wrong to me.. thats not to say that MO functions like quant and market risk aren't relevant experience for a trader to have - it's just to say that being a trader an extra X number of years equal to the amount of time you spent in MO would be better experience for trading intuitively.. and its hard to see how other BO/MO functions would be a valuable background for trading
in any case.. your exit opps are always greatest at a bulge bracket, thats just the nature of the game.. you join a boutique shop so that you can do something you couldnt otherwise do at a BB (like prop now), or because you like the culture there better (smaller group, etc), or simply because you think you'll make more money there.. but i would caution you from taking a job at a small shop with the hope that one day you'll have the opportunity to go to a BB.. thats not to say its impossible, its just to say the flow tends to be BB-->boutique and not the other way around
really it's very difficult to assess all these things without knowing exactly what kind of a desk you'll be joining.. it is not necessarily true that if you're not joining a BB that you'll just be covering custy trades.. any chance you could name a competing firm or call up these people who have given you an offer and figure out what you're getting yourself into? it just seems like you don't really know and that's not a good way to go about making career choices! we can all talk on this forum about hypothetical functions and exit opps but its all sort of meaningless since no one, including you, seems to know what this job is!