Indeed, unfortunately kernels are very dependent on your device, ROM, and your usage patterns. So it is impossible to say what is the best. I try and flash as many different kernels as I have time to try. Also some of the developers make pretty radical changes between versions of their kernels, so say I didn't have a good experience on version 8, version 9 could be much better.
There are a lot of different kernels out there. Lean, Franco and Faux may be some of the more popular ones, but Apex, Glados, OhHeyItsLou, Codename and many other kernels exist and have their fans. Another thing to consider is different kernels have different features present. Like different slots to underclock/overclock, different governors, color control options, undervolting, different networking options and some other things. Do you want color control? If so, find a kernel that offers that ability. Do you want to hotplug, or use some of it's offspring (like hotplugx, conservativex, interactivex, performancex on Lean Kernel)? If so find a kernel that offers that.
If you are after stability you may want to stay away from experimental or beta kernels and features. Overclocking (and underclocking below 350MHz), undervolting, and hotplugging can all potentially cause problems even if for the most part they can be stable.
I, or someone on these forums, can help with specific questions. But the best kernel for you is going to be subjective to your device, setup and usage pattern
