Usability research on tree navigation vs search

I'm working on a mobile app that will display specialized, highly structured contents to professionals. The objective of this app is to be a tool helping them in their work. So the key element for them is to find the relevant information as quickly as possible.

The current prototype allows users to navigate through categories and scrolls alphabetical lists to access a specific content. They can also use specific filters to limit the number of elements to scroll through. To give an idea, there might still be up to 50 elements left even once filter / category are applied.

There is no possibility to filter on multiple criteria at the same time, nor full-text search. The main stakeholders resist implementing these features.

Intuitively, I would think that full-text search would be quicker than navigation, even (or especially) for expert users, to find the relevant specific content they are looking for. But maybe I'm wrong.

I read articles regarding search vs navigation, but they are mostly relevant for web users discovering a website, rather than experts in a professional context, with regular use of an app.

Do you know if usability research has been done in a similar context, which would show the difference in task completion time of browsing vs searching?

PS: the current prototype is static with limited contents, we can't do a usability study of this nature with it.