What are the differences in term of features between Cfengine and Chef?
Chef has much greater integration with "cloud" VM hosting providers, and a greater amount of recipe sharing than CFEngine.
CFEngine takes less resources when it runs, and runs on a much greater range of computing environments from embedded devices to supercomputers, and on a lot more operating systems -- it's just a few small C binaries and a couple of C libraries, so it is more portable.