Recently Performance Tuning compared Oracle 10gR2 RAC on Windows Server 2003 x64 vs. RHEL. You can download the paper from microsoft-oracle.com
The following behavior was observed during testing of the Oracle RAC databases on Red
Hat Enterprise Linux x86_64 and Microsoft Windows Server 2003 Enter:
Oracle RAC Stress Test
o Transactions Per Minute were roughly equivalent for 2 - 150 user sessions.
o Transactions Per Minute were up to 16% higher for MS Windows for 150
- 250 users.
o CPU usage was above 90% for all of these tests for both Linux and MS
Windows Server.
o The response times for the “New Company Registration” test component