Detailed look at OpenOffice vs MS Office on a Terminal Server by Bernhard Tritsch:
The results show that roughly 30 to 40% more users can sign on to the platform with Microsoft Office 2003 than with OpenOffice.org 2.1 with identical hardware and an identical configuration of the terminal server on Windows Server 2003 SP1. Even for terminal servers with Microsoft Office 2007, one can expect that the system resources can be used roughly 20% more efficiently than is possible on a system with OpenOffice.org. This applies both for the 32-bit and the 64-bit version of Windows Server 2003 when used as the primary platform.
Memory requirements of all three Office Suites on 64-bit Windows Server 2003 are increased by the factor 1.1 to 1.5 if compared to the 32-bit platform.