What Path Leads to a More Fulfilling Life?

This is an incredibly subjective question.

The vast majority of extremely wealthy people are completely miserable.

That question poses a false dichotomy - for several reasons. First, there are MDs and Partners at MM and boutique firms who "kill it", and partners and BB and PE firms who are fairly mediocre and rely on their firm name to generate business (and the lifestyle between the two categories aren't that different).

Second, you can be happy with a great family and friends while "killing it" - in fact, I would argue that the many of the most successful people need to maintain both because it is difficult to sustain great relationships with clients or portfolio companies if you aren't happy with your home life. Even within the same office at my old jobs, there were VPs and MDs with great work life balances who knew how to manage people and still have a great reputation at work, as well as those who worked 24/7 but were fired because they weren't good at their job.

Take this with a grain of salt, but I've always thought that as you get senior, you need to push back on setting a reasonable work life balance for yourself. That doesn't mean you shouldn't work hard - there is a difference between working until 4am near the end of a deal as a VP because the bid is due in a week, and missing your daughter's graduation or your friend's wedding for a pitch for initial bid. As an analyst, things will be crazy, but even then most groups are reasonable about big life events (of course there will be exceptions), but over time your bosses will respect someone who (1) has a life and priorities, and (2) is not a complete pushover - as long as your work continues to be excellent.

I think there is a problem with the assumptions you are making. You are giving us the options to choose between making a "few million" per year with what sounds like a lot of free time or making a bucket load of money (I don't know..100 million per year?) without any free time. First of all, you will most likely not casually be paid a few million a year without having to work your ass off (except if you're the founder and now act as non-exec chairman or something along those lines). The guys at my firm who pull in 1M+ are constantly working even when they are not in the office.

All else aside, I'd go with the boutique / MM partner role. There is very little you can't afford while making that amount of money (and everything else you could rent). What's the point of accumulating a fortune if you can't spend it or put it to work for something good?

I don't think (or at least I hope) nobody bases their happiness off whether they are an MD or a rainmaking PE guy. Your happiness is going to depend on:

a) do you like your job - presumably yes for both of the above b) are you getting what you need out of it (i.e. competition, high profile etc.) - again, probably yes for both c) enough money to live comfortable and do whatever you want to do - yes to both d) social relationships fulfilled - this is highly variable and dependent from person to person but also one of the key variables for happiness, and also impossible to determine based on your scenario.

In short, stop worrying about money and whether you're at KKR, UBS or a small regional place. Tick all 4 boxes above and you'll be happy.

While doing well in your job can make you happy, it's highly unlikely that you need only a career to be happy. You have to have balance in your life. You can be the guy who makes a few million a year but maybe you spend more than that because you want to impress people. It's safe to say that you probably won't be truly happy. While I think there are flaws with minimalism, I think most people would benefit by reading about it/learning more about it. I'm not a minimalist by any means but after a bad breakup I read about it and it helped me to realize that more money or more things won't actually make you happy if you aren't already happy. Here's a link to two guys who I think make it easier to understand - http://www.theminimalists.com/minimalism/. Again, not suggesting anyone become a minimalist, but reading about it might offer a different opinion than what is normally displayed in American culture.

A Starbucks sipping hipster who majored in philosophy can better answer this question for you. Find one at your nearby Starbucks who is typing into his/her MacBook.

on average? I'd say being the principal of a boutique firm.

i'd say the absolute happiest one would be a dealmaker at BB's and PE shops.

This is so subjective. The most fulfilling thing in my life would be ending mass incarceration and ending insanely abusive laws like the sex offender registry (lifetime status for peeing in public, taking a photo of yourself as a minor, streaking, intercouse on beach, etc). But I wasn't born with a trust fund and need $$$ before politics. You have to find out what appeals to you and pursue that after laying the groundwork and gain the knowledge/ skills/ money to accomplish your dream.

Neither. You have to be a partner at a HF pulling in $50mn/year. Otherwise you're going to be a sad, little miserable fuck who no cares about /end sarcasm.

In the end, most guys don't end up on Wall Street.

Certainly not people in S&T