Following up the last post on why selecting a younger, energetic firm (such as Modative) can be an advantage over going with a more established firm. Here is something that we have always considered an advantage:
Larger, more established firms often have many more projects and larger staffs. This is not necessarily a good thing for you as the client. With those many projects and staff comes less attention to your project. The principal (boss, lead architect) that you initially met with, will probably have very limited time on your project. They will often hand it off to someone lower on the totem pole to manage, such as a project manager. That project manager may even have most of the work done by someone even lower on the pyramid, a draftsperson or intern. The quality and attention you receive will no doubt be somewhat diluted.
In an office such as ours, there is no grandiose hierarchy. The principals you meet with with manage, design and most often perform most of the work on your project. That kind of attention is hard to beat.