Снощи на SUGBG срещата се зададе този въпрос. Отговора е, че перформанс-а е по-добър и възможностите за скалируемост са значителни. Ето го директно от блога на екипа на SharePoint в Microsoft: http://blogs.msdn.com/sharepoint/archive/2009/05/07/announcing-sharepoint-server-2010-preliminary-system-requirements.aspx
Q: Why are you only supporting the 64-bit versions of SQL Server 2005 or 2008 for SharePoint Server 2010?
A: This decision was based on our current test data for SharePoint Server 2010 and real world experience from customers running SharePoint Server 2007 with 32-bit SQL Server. SharePoint performance and scalability can benefit significantly from 64-bit SQL Server and the throughput increases are significant enough for us to make the difficult decision to only support SharePoint Server 2010 on 64-bit SQL Server 2005 or 2008. It has been our strong recommendation for some time that SharePoint Server 2007 customers take advantage of 64-bit SQL Server due to the inherent performance and scale benefits it can provide.
Q: Where can I find more information on the advantages of 64-bit hardware and guidance on how to migrate SharePoint from 32-bit to 64-bit.
A: These two TechNet articles are a good starting point;