Hi,
If you having an infocube which having data which is sufficient for reporting then you can go for BEx Reporting based on this infocube.
But Consider if Reporting requirment is having report on data which belongs to multiple InfoProviders like InfoCubes/DSOs then its better to go for MultiProvider. Its Doesn't store data physicaly. You can apply conditions as per requirment on your multiple Infoproviders, fetch the data into MultiProvider and finish your reorting requirment using BEx.
Hope this Helps.
Thanks,
Santosh.