Pros/Con of Excel VBA v SQLite

I am recently working with a relational database program that has been written in Excel VBA. Excel VBA was chosen as it is a default application on computers where I work and therefore everyone would be able to use the database.

As part of the database development the need has arisen to add some more tables which will only interact programmatically with the current database. In order to consider all my options I am contemplating separating this new data either as an SQLite or second excel file.

I keep changing my mind as to what would be the best route and would appreciate information from those who work with the programs.

The new database would need to perform normal database functions quickly and efficiently. Given this context what are the advantages/disadvantages of using SQLite compared with excel?