Hello, I currently work a top strategy boutique in Europe so I will share my insights on why a boutique can "beat" MBB
1/ Strategy only (at least for my boutique, but others may focus on marketing etc). As such, you can really focus on the area you like. This is often what my friends at MBB are "jealous of" as I can brag about my strategic plans, growth strategy, due dil etc.
2/ Personal growth & visibility = there are less people and support staff working at a boutique as such you can really grow hyper fast depending on your skills / appetite. However, it can also be "negative" as you will have to do a lot of things "by yourself" and "figuring it out" (market research, admin tasks, etc.). However, you really learn to be independant. Finally, day one as Junior Consultants you are given responsabilities (and not only taking minutes)
3/ Knowing each personal individually. I can tell you all the consultants know each other, eat lunch often together etc. You can really create some nice connections whereas with bigger firms you always meet new people which means it's hard to create lasting friendship
4/ Entrepreneurial aspect: I wanted to a pitch the CEO of a large company so I asked my MD if we could do it and we actually did it! This is truly a highlight for entrepeurial profiles. You can start any initiatives you are interested in (of course if it fits the firm goals) whereas in MBB it's harder to start big initatives like this one.
All in All, I really enjoy my time at a leading strategy boutique and I can tell you the learning and work is not very different from Tier 2/MBB. As I am leaning towards "senior positions" I am often approached by headhunters and HR from MBB/Tier 2 so if the end goal is MBB, a few years in a top boutique can defintiely help you get there.
Best of luck