for making such a decision, you have to consider lots of factors like 1. the kind of data you are going to store 2. the type of data 3. the approx size of data and the expected growth of data 4. usage statistics 5. kind of interface - mainframe, unix etc
These are just some factors. for more details, you can contact Veronica.Chong at teradata dot com
also, check out the Forrester report on Teradata. You can get some insights from that. http://www.teradata.com/t/WorkArea/DownloadAsset.aspx?id=10115
Personally, I will say Teradata is lot better than Oracle if you want to have a good and robust DWH system.