1. Let's state the obvious: IT'S FREE. That's a huge deal for a lot of cultural heritage institutions right now. There just isn't always money to dedicate to a new system. And if there is money, there might not be enough. Or the institution really needs to prioritize something else over your project. Either way, a free tool is always a plus.
2. It's open-source. This allows for a much greater level of customization than some out of the box tools. For example, I could create a metadata schema to build the system around and customize user interfaces. Another bonus to this is that users/developers share their code/documents.
3. CA allows for (perhaps even focuses on) item level description! This is a huge deal for me since I'm creating a database that needs representations for each historic property and its corresponding site card.
4. Data entry can be performed through the cataloguing back-end (Providence). This tool is user-friendly for any staff member with a little training.
5. Data is stored in the MySQL database the user sets up on which the Providence tool runs. This means that catalog records exist on your server and would be retrievable if CA failed or you decided to move on to another product.
6. Pawtucket (front-end, web-publishing tool) is extremely visual.
7. Users can register/login. This is important to me since I'll need to create the ability for surveyors to electronically submit their survey results to us in the future.
8. CA support staff/developers are extremely helpful! I've worked with two of them (Seth and Jonathan) and both responded to my requests in a timely manner and made themselves available on a regular basis. On top of all of that, the forum is a productive environment for troubleshooting and problem solving.
Once I've presented the website to my colleagues in Historic Preservation, I might be able to tell you a little about the cons from their perspective if there are any.