My spelling is not the best. Swizzle, Sizwheel, whatever?
They work in conifer just fine. I would think they would work better in conifer than hard wood, because conifer wood fiber flex's much more than hard woods. However, like Ive mentioned before. I have little experience with hard woods. Also, I don't use a swizzle that much at all. In fact,
I'd much rather just face up any leaner, throw a deep buck cut in it, set a wedge with the quickness if nessasary, pull the saw out if the kerf. Find a good tree behind the tree I've just crippled, and use the tree behind it to drive that SOB over! No Jacking, no wedging, no swing cuts, no swizzle, cuts. Just straight up mow'n em down!!!
Cut safe, stay sharp, and be aware!