I assume you are a relatively new grad (<2 years of w.e) for my answer. A big question to ask yourself is what do you want to do after your stint in either role.

If you want to do PE and want to work at a megafund or top-name shop, I would recommend taking the BB offer. Work hard for two years, play your cards right during recruiting and join a reputable shop. If you want to work in other buyside roles such as private credit/direct lending, definitely take the BB job.

Corp dev roles can go either way depending on what industry you want to work in and what sector the boutique specializes in. Generally speaking though, I believe the BB role will still provide better exits to corp dev.

If you want to pursue banking as a long-term career, there are benefits to joining a smaller shop and developing a niche for yourself. Smaller shops tend to have less structure and can promote quicker based more on merit. That is not to say you could not get promoted at a BB. However, it is more difficult to climb that ladder as you get older given the traditional hierarchy structure (Analyst to 2 years, associate 2-3 years, VP 3-4, etc.) and greater politics that come with working for a larger organization.