SpeedMod K3-9 = latest Samsung 4.0.4 kernel (-) MMC_CAP_ERASE (+) r00t (+) custom recovery
So SpeedMod is a *safe* kernel, and is developer ready.

The kernels you meant to ask about are the "AOSP" kernels. They're pretty much a new, entire kernel built from scratch using code from different sources. They are always inferior to OEM kernels in terms of stability, battery life, performance and features. However, as development proceeds it gets the missing features and more, gets more stable, more smooth and saves more battery... becomes and overall more efficient kernel. And they support third-party [ROMs] that have more customizations/features than OEM Roms.

If you have to ask "is it worth it" then you've answered your own question. Until you ask "I need this feature" or "how do I do this", then you might begin to investigate and understand a little further, changing your question into "how can I flash it" and "when will it be ready".