For Oracle BI you have to use the Oracle data integrator, which ideally a software engineer would use. With Power BI, you can transform and clean your data with about the same knowledge curve as a power user of Excel. The chart interface with Power BI is easier to use. I would improve the Oracle BI charting to make it easier. I would also improve the process to develop ad-hoc reports. To view the development of an ad-hoc report, you have to pass a date parameter.