Canva is a great tool used by millions of people looking for a DIY solution.
Penji, on the other hand, is a service best used for those who do not want a DIY solution, OR simply do not want to do all of the creative and design work themselves.
Both can be used well, if done right. They can also be used individually.
The question isn't so much how each company is different from one another, but more so the benefits of both organizations working together in unison.
We do offer Canva delivery within our Agency subscription for all clients.