What do you mean "Dashboard data" - graphics? Status indicators, scorecards??
All these options mentioned by you are valid, depending on your business scenario.
Example: If your data comes from SQL and via PerformancePoint designer you built you dashboard based on KPIs - you are stuck with SharePoint.
You did forgot one very powerfull - POWERPIVOT (free for Excel) and even more could be installed and configured on SharePoint 2010 which would enable Analysis Services to process your data directly either from SQL, SharePoint, Excel Services and COMBINED!!!
Hope it helps,