Fijian kava has definitely been my staple; plus, it may be imagination, but I almost swear that pure waka doesn't give me dermo, or at least not as easily.
The Savusavu is super strong, but I find it makes me sleepy about an hour into it; like I want to lay down on the couch and sleep. Its funny, but I find the Kadavu heavier in effects, no Kavain rush and more muscle melting, but it doesn't necessarily make me want to close my eyes and sleep.