OK, I found the cookbook that you are referring to. Not sure why the link did not take me to it, but found it anyway. When I look at the recipes in the cookbook, they are comparable to commands in WFA, not workflows. So comparing the two, I see 11 recipes compared to 100+ for clustered OnTap in WFA. To be fair, the chef recipes look like they do both create and delete objects, so these are more like 22 WFA commands. They do not appear to show or modify objects. The CHEF cookbook has all of the basic NetApp objects, like volumes, aggregates, lifs, users. It does not have anything for SnapMirror, volume moves, QOS and a few other things. So just based on automation content, I would say WFA has more feature/automation capability. A workflow is a collection of commands, as well as finders and filters from the WFA database. So WFA workflows are capable of making selections of resources from the data in the database. I suspect the chef cookbook would need specific input to perform basic functions. The volume create recipe for instance requires the aggregate. The aggregate recipe has only create and destroy, so I do not see how chef would be able to collect data to determine which aggregate had the most available space or did not exceed a threshold.
As for the pro's of chef, I am not that familiar with the product. It does look like it can automate most anything with a cookbook. It just looks like the netapp cookbook is limited.
Mike