In the CURRENT SEAHAWKS SYSTEM, Pete's way, I'll go with Kam over Easley.
I don't remember Easley ever knocking over a 300 lb Offensive Lineman and then tackling a running back. I saw Kam do that against the Cardinals this season. And it wasn't even that unique a play for him.
Easley would hit Vernon Davis, but would be about 30 lbs lighter than Kam and Easley would just "hurt" Davis rather than leave Davis "...as God is my witness...HE IS BROKEN IN HALF!!" the way Kam did.
Easley would have instilled mortal fear in the Wes Welker's of the world, but not so much in the Demaryus Thomases of the world. They both piss their britches when they think Kam is around.
So, in the current Seahawks system, Kam is clearly the choice.
In every other, more conventional system, with more cover responsibilities, Easley would be the clear choice. In a pure cover situation against a WR, Easley was a better cover guy. Kam's good at it; Easley was great, and had terrific ball skills and closing speed. It's more like Easley is a perfect blend of Earl Thomas melded with Kam Chancellor, except with superior ball skills over that hybrid. Range, speed, power, hitting, turnover-creating, smarts, QB reading.
Both are game-altering talents. Easley in his prime would be the starter and play at an all-pro level at SS and/or FS for just about any current NFL team. Gotta think though, that he might add 10 lbs of muscle today, without losing speed, just in overall training method improvements.