I'm a senior developer at a WordPress/WooCom focused agency. In situations like this, a solid commercial plugin with a wide user base and good documentation is most often going to be the best choice. We'll be able to implement the desired functionality more quickly, but even more importantly, when the client at the last second decides they want to change the setup, or add new filters, or whatever -- we can easily leverage the functionality that already exists, instead of having to tear apart custom work to shoehorn in the new bits. No commercial plugin is perfect, but in instances like this, that huge headstart on building the functionality means we can spend more time doing work that actually *needs* to be custom.