From a user's perspective
For most users, they can work from your CRM - they have access to all of the important functions in regiver right there on the contact record. They don't need to open new tabs, they don't need to pop up new windows. It's nice to use and they can quickly do things like donations, cancellations, upgrades, downgrades and more.
For the finance team, they will spend time in regiver proper - all the tools are there for them to manage regular giving, produce GL reports, reconcile direct debits, do batch income processing.
All the while regiver will be sending back and forth information to your CRM to make sure when a user looks at a contact in the CRM, they can see the complete giving picture.