ALV reports give a flexible on-screen display, sorting, filtering, subtotals, built on top of custom or standard ABAP logic, and they're what a developer reaches for when a standard transaction report doesn't quite fit. Report Painter takes a different approach, letting a finance team build its own report layouts, a custom balance sheet variant, a specific cost center view, through configuration rather than code.
Plenty of day-to-day reporting runs through named transactions built for a specific job: an open PO report, an aging report, a cost center report, each with its own selection screen and output. For bigger cross-module analytics, SAP BW handles the data warehouse layer, and BusinessObjects (often accessed through WebI) sits on top as the business-user-facing reporting and dashboard tool.