Hi Hrag,
an established consulting brand makes definitely easier to join a top MBA; moreover, in many countries, MBB and other top brands can sponsor MBAs to top performers, while boutique consulting companies normally don’t do so. Having said that, it is possible to join a top MBA even coming from a boutique. The likelihood of such transition depends on the brand of the boutique – you should be able to get an idea looking at the alumni of the company on LinkedIn and considering how many proceed their career with an MBA.
Best,
Francesco
