First, for an area where there are visual differences between the four Enterprise Linux distributions is their artwork/desktop. Here's a look:
One note about the Oracle Linux 6.2 release is that it was the only one of the four to have mode-setting issues. On the Core i5 2520M Sandy Bridge notebook the resolution was defaulting to 1024x768 unlike the native 1600x900 resolution on the other EL-6.2 installations while the Linux 2.6.32 and xf86-video-intel 2.16.0 DDX were still in use across. For the Core i7 3960X Sandy Bridge Extreme Edition (Sandy-E) system with the NVIDIA GeForce 8600GT graphics, the VESA driver was being used, as Oracle Linux is not shipping the Nouveau KMS support.