How is it safer and in the future api or database connection?

Question

Yii

I use a project where it is written in yii2. frontend has already been written There are 2 projects 1 CRM second training portal for employees. You need to make a relationship so that all employees from the training portal are recorded in the contacts section in the CRM. At the same time, authorization of users in the CRM goes shopping, and in the training portal, authorization by employees.
I think it would be safer and more correct to use the api for the training portal and the CRM simply takes this data and uploads it to its contacts, then there is a question about the information, because the full name and position of the employee are recorded there.
The second point is not to use the api, but to use the connection to this database in the CRM, then you will have to create models and build the relationship between the user model and the position, which, in principle, is additional work in the CRM.
If we take it for the future, then the front is planned to be rewritten to the js framework and there you still need to use api. But if you use the return of data for a specific site, then I have a question about the caution of confidential information. Which path is better to choose?