Read these two:
Basically, I don't think that Fedora tinkers too much with the vanilla kernel. Some fixes, some driver here or there, but that's about it. Debian kernel on the contrary are potentially more different, though it depends on the version I guess.
The Debian policies are much stricter than 99% of the distros out there. If some piece of code has the slightest licensing issue, it's removed. That means that, potentially, the Debian kernel supports less hardware and features. Note that I really mean "potentially". I have no idea on how code do they remove from the kernel.
Their emphasis is in the security area. Most of the patches that Debian adds to the kernel are to fix some security issue.
However, it really doesn't matter which distro you choose. If you really want to use Debian you can download any kernel from www.kernel.org
and compile it yourself. You can also add any patches you want, as long as they are designed for your version of the kernel and do not interfere with each other.