What is the difference between use 'force:showtoast' and 'lightning:notificationsLibrary' showToast method as strategy to displays toast messages?

In developer doc follows this recomendation: We recommend using lightning:notificationsLibrary for displaying messages in the app via notices and toasts. (https://developer.salesforce.com/docs/component-library/bundle/force:showToast/documentation)

I wish to understand why.

Hello, I'm using salesforce cli to run basically "sfdx force:source:retrieve -m Profile:Admin", which I know technically sfdx is not that much compatible with profiles but, on a sandbox on a project, I got the object permissions and all that, but running that command on other sandboxes and my developer org brings only the user permissions, is that related to some org config or something? I'd love to know because I kinda like to use sfdx source for all I can.

 

Thanks in advance, hope someone can help me out on this