Ive never tried Knoppmyth myself before, I just saw it being used in the creation of a HDTV capable MythTV box on that tech show "systm" (The same guys who made "The Broken").
I figured that since Knoppmyth has wizards that speed along the installation process, it should save you time, but if your needs require you to tinker, then by all means stick to gentoo. Thats what its made for after all.
Case in point: I would love to use a simple binary desktop distro for my laptop, because of the constantly changing environment a laptop is usually in. But since my laptop has a funky combination of hardware, no matter which distro I choose, I would have to tinker to get it all working. So I stuck with gentoo for my laptop.
For my desktop, gentoo all the way of course.

(That goes without saying...)