Intel Sandy Bridge graphics on Ubuntu 11.04 are still broken while with Fedora 15 the SNB experience is decent thanks to back-porting some of the DRM work and using Mesa 7.11-devel over Mesa 7.10.2.
With the ThinkPad T61 bearing the NVIDIA Quadro graphics, the Nouveau driver was used under each OS. While GNOME Shell can cause a performance degradation, Fedora 15 still had a much higher frame-rate than Ubuntu 11.04 with the Nouveau graphics. Again, Fedora 15 back-ports more of the kernel DRM driver code and they are using the Mesa 7.11-devel code rather than the months-old 7.10 code from last year.
With the R300 Gallium3D driver for the ThinkPad T60 and its Mobility Radeon X1400 (R500 class), the Fedora 15 performance was slightly better than Ubuntu 11.04. Again, that is not to any surprise.
As is expected, under Nexuiz, Fedora 15 continues to perform much better than Ubuntu 11.04 and its older open-source driver stack.