What are the benefits of having multiple front-ends?

TL;DR When should a project have multiple front-ends?

I'm unsure if we should extend our existing front-end or make another one with additional functionalities.

We have an Ionic-React app that interfaces with a Django back-end.

We've reached a point where we need the following:

1. An admin front-end (with some admin-level permissions). Think support desk, account overview, and analytics.
2. A desktop app (with limited permission). Think account overview, but with less permission than the mobile app.

Would it be better to merge these 2 solutions into our main mobile app (and use ionic to generate a PWA) or should we have a dedicated solutions for these?

Disadvantage of merging:

1. The app will be heavy. Ionic is known to be slow (and sometimes buggy).
2. User permission will be quirky. Admin and desktop app have the most overlap in functionality, so it would keep the code much cleaner.
3. 2nd front-end could double as landing page.

Advantages of merging:

1. Less code to maintain, less front-ends to deploy. I honestly can't think of another advantage for this. This might be really messy...

Which solution do you think would work best?

As you can tell, I want separate apps, but I have a project manager to convince...

Any advice is greatly appreciated.

Thanks in advance :)