How to set up Diffusion repositories for a remote monorepo?

Let’s say you want to configure Diffusion to monitor a remote SVN monorepo. Would you configure one Diffusion repository for the entire monorepo, or a separate repository for each logical project? (Or taking it to the extreme, each branch of each project?)

Initially, we configured a separate Diffusion repository for each project, but now we are seeing performance problems on the SVN server. I suspect a single Diffusion repository for the entire monorepo would yield better performance because we wouldn’t have a bunch of separate repos polling the SVN server.

Does anyone have experience/advice about this problem?