Open Web Analytics offers a feature comparison page: http://www.openwebanalytics.com/?page_id=158 http://www.openwebanalytics.com/?page_id=158 I'd be most con

Open Web Analytics offers a feature comparison page: http://www.openwebanalytics.com/?page_id=158 http://www.openwebanalytics.com/?page_id=158 I'd be most concerned with scaling. Piwik doesn't really scale off a single server. Open Web Analytics lets you distribute the recording and queueing of events across multiple servers, but you still have to process stats on a single server. I'd stick with a hosted solution for any high-volume project - it'll be cheaper in the long run. I'd only make an exception if you need a feature that the hosted solutions don't offer, in which case it's probably time to suck it up and start building your own analytics. There is certainly room for open-source analytics designed with scalability in mind - perhaps with something like Cloudera's Distribution for Hadoop as a backend.