I mean if I were to just assigned DBO to both MSDN and the vCenter DB for the easy way out. However as security and user rights has become a concern at many customers' requirement. I tried going through the installation guide to setup database with just enough rights but no DBO.
The bad thing is its a lot of work to do it manually following the guide. The good news is VMware has provided the script however some work need to be done to customize to your own needs.
Here my setup is on Windows 2008 R2 with SQL Server 2008 R2.
For MSDB, you can assign the DBO directly instead and remove it after installing vCenter and Update Manager. Yes you hear me. Do not remove the DBO rights on the vCenter user till you are done with Update Manager. This is so as Update Manager installation also require access to MSDB.
You can definitely assign dbo to the vCenter database or just the required base on the script.