The Tremulous results are interesting and somewhat different. The Intel driver was 18% faster when Compiz was not in use, but this time the Radeon + KMS-DRI2 driver wound up being 54% faster when Compiz was in use rather than Metacity. The Radeon + UMS-DRI1 performance remained the same regardless of the window manager. The Catalyst driver once again performed the same regardless of whether Metacity or Compiz was being used and when it came to NVIDIA graphics this is the first game where Compiz did not affect the frame-rate performance.
Intel again comes out a Compiz loser with Urban Terror where its frame-rate drops by seven FPS. The modern Radeon driver was 17% faster in this test when Metacity replaced Compiz. With the other hardware/drivers, Compiz had no major impact on performance.
With the Catalyst driver, we see the best performance by the Catalyst driver is actually offered when Compiz is running rather than Metacity -- it is a speed-up by about 12%. However, the NVIDIA driver again fails with Compiz where its frame-rate drops by 16 FPS with Compiz.