Actions on Google will likely take off much faster than Alexa Skills. Yesterday, I wrote about this being the case because there are more potential endpoints for Actions — Android devices, Chrome TVs, and Google Homes — than there are for Echos.
However, there’s another simpler reason. The bulk of the work for developing Actions has already been done by developers who have made thousands of Skills for Alexa Skills Kit. The work to migrate these to Actions is nominal compared to the initial effort to bring the API or service to Alexa.