1. Its price! The PowerBI Pro goes for only 10$ a month/user
2. Its simplicity for designing reports and dashboards
3. Its rich (and evolving all the time) community Add-ons
4. Its complete Software As A Service concept. Simple deployment.
It realy depends in your needs. It may serve as an E2E tool but, at some circumstnaces you will need to add - Data Warehouse, Paginated reporting tool, M/L tool, Data prep tool etc.
