Choosing between MBB

Caveating all of the below with a disclaimer, which is that I work at Bain, so I'm certainly biased. Chose to work there while turning down a McKinsey offer almost two years ago.

Bain Capital has nothing to do with why Bain is a better firm for those interested in PE. McKinsey actually sends as many people to Bain Cap as Bain does (although this is largely because McKinsey is way bigger).

If you really want to go work in private equity, there are a number of reasons why Bain is slightly more conducive to that. Bain is the clear market leader in private equity due diligence work, with McKinsey a distant second, and BCG well behind both. At Bain, you can do a PEG (private equity group) rotation where you spend 6 months doing nothing but private equity consulting, which goes a long way towards making you sound more intelligent during a buy-side interview. You can't do that at McKinsey/BCG because they don't sell enough private equity work. You also wouldn't want to because due diligence work is often a shit show at those firms because they don't have as much expertise in it. Doing a 3-week diligence without any prior experience doing one is pretty rough, and being able to leverage frameworks from previous deals goes a long way towards making a project with short turnaround times a lot more sustainable. Don't believe me? Ask anyone at McKinsey or BCG about doing a diligence project, and at best, you'll get something along the lines of "I'm glad I did it, but I never want to do it again", and at worst, you'll hear "it was the worst experience of my life". At Bain, people love doing PE work, and demand for those projects often exceeds supply from a staffing perspective.

Add all that up and throw in a little self-selection bias, and you end up with way more people from Bain going into private equity than from the other two firms on a %-wise basis. With that said, if you're committed to going to PE, you can certainly do so from McKinsey and BCG as well, so I wouldn't base my decision solely off that.

As far as exit options more broadly, everyone at McKinsey Bain and BCG gets emails every week from the same damn headhunter firms. I went to two recruiting events in the past week, one for a VC fund and one for BizOps with a large tech company, and all three firms were extremely well represented at both. You'll have great opportunities no matter where you go.

Ultimately, the largest driver in your decision process should be where you like the people the best. In the short term, you're going to be spending 5000+ hours over the next two years(conservatively) working with people from whatever firm you choose, so go work with the people that make you feel the most comfortable. Over the long term, your colleagues have the potential to be part of your social and professional network for years to come, so go work with people with whom you really feel excited about that prospect.