I’ve used most of the popular ones. Asana was also good, I’ve also used some bigger ones such as InfusionSoft and Zoho but they are overkill for a small business. Monday is nice and visual, good app and ideal for a small SEO agency.
You can import Asana projects into Teamwork. I’m new to it but I chose Teamwork over Asana because you can switch back and forth between list views and board views in Teamwork. I didn’t want to be locked into either one.