Power BI is an interactive tool for visualising data.Power BI can connect to different types of data source like spreadsheet, sharepoint list, database or even connect to tables from a website.Power BI reports are published to Power BI cloud service which can then be accessed privately or anyone within the organisation or even public depending on security settings.Power BI reports can be accessed from anywhere (Desktop, Tablets and mobile). 

Excel is a great ad hoc reporting tool. Visualisations are highly customisable. Excel natively supports sparklines .