Personally, I would also choose for the 2012 exams.
Your knowledge will be up to date and ready for the future (SQL Server 2012 will be released soon).
And, if you know the material for the 2012 exams, you also know the material for the 2008 exams.
(SSRS and SSAS multidimensional haven't changed much between 2008 and 2012)
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MCSE Business Intelligence - Microsoft Data Platform MVP