Speaking entirely for myself, opinions my own, may not reflect my employer etc. etc:
I came in to this job expecting OL to just be a CentOS clone, and not really expecting much from the kernel they ship with it.
It is both a CentOS clone, and a bunch more. Oracle takes the CentOS packages and applies bug fixes etc. that upstream RedHat has failed or refused to apply, so I've actually found OL to suffer from fewer problems than CentOS, and we've even had to apply mitigations for CentOS 6 for stuff we haven't had to do to any other OS we distribute. For entirely selfish reasons, I was really glad to see CentOS 6 go end of life last month.
On top of that the OL team hires a significant number of upstream kernel developers, including the core maintainers for a number of components, like XFS, Xen, and so on, and produces the Unbreakable Enterprise Kernel (a really curious choice of marketing terminology), that incorporates mainstream bug and security patches, while being closer to mainstream than RHEL/CentOS, and the kernel patches submitted upstream by OL devs.