I would go with kinefx. It is way more in line with the Houdini mindset. Granted some things might be a bit harder to understand but they will be improved further on. So you invest in the future. The traditional bones on the other hand are legacy and won't get any updates.
Thanks for your feedback about this domain ! I begin to think the same thing because KineFX is better at every update and it seems to be the future for complex rigging...