Scientific Linux 6.3 and Cent OS 6.3 both have 18.104.22.1689 kernel. Cent OS is the most popular web server and I own the latest version. Scientific Linux has enhancements like NTFS-3g, Andrew File System, and more security.
Cent OS 6.3 delivers:
• Significant improvements in resource management and high availability.
• New features aimed at storage and file system performance.
• Identity management functionality.
• Technology integration with VMware and Microsoft environments.
The key benefits for organizations deploying CentOS 6.3 are:
• Greater efficiency via resource management and performance optimization.
• Enhanced business agility through additional security enhancements.
• More flexibility for virtualized and clustered environments.
• officially supports allocating up to 160 processor cores and 2TB of working memory to guest systems; previously, the distribution only supported 64 cores and 512GB of RAM
• support for SR-IOV-capable (Single Root I/O Virtualisation) networking hardware
• evice Mapper, which is used by the Logical Volume Manager, now offers the Thin Provisioning features that were integrated in Linux 3.2
• SCSI target via Fibre Channel over Ethernet (FCoE)
• features that allow RAID levels 4, 5, and 6 to be implemented via the Logical Volume Manager (LVM); to do so, LVM accesses the kernel’s software RAID code, which is typically managed via Mdadm
• graphics drivers in the second release candidate of Linux 3.3
• the RDRAND x86 instruction support