Comparing the same Visits report using the SiteCatalyst interface or the Data Warehouse, tipically results in different numbers. As known, it is due to Visits that took place very close to midnight (12PM): while SiteCatalyst attributes them to the day 1 (the day before the midnight), Data Warehouse attributes them both to day 1 and 2. So if for example a Visit took place from 11.40PM untill 12.10PM, SiteCatalyst counts a Visit for day 1 while Data Warehouse counts a Visit for day 1 and a Visit for day 2.
Furthermore, a similar issue take place when comparing the same Visits report using the SiteCatalyst interface and Discover.
As known, it is due to the different ability of SiteCatalyst and Discover to recognise the users: while Discover is able to track visits with persistent cookies disabled, SiteCatalyst can not. In this way, Discover tipically shows a higher amount of Visits than SiteCatalyst.
It would be nice and more user-friendly if the data (or the same report) wouldn't be different even if using different "tools".