So I haven't network rendered with AE in years (generally because it stinks). So I thought I'd give it a go today. I used two 8-core Mac Pro (both with MP turned on) and my render time was exactly the same as if I'd rendered it locally with one 8-core. I rendered to TIFFs, and used "skip existing files".
Look at "Current Render Details" in the Render Queue to see what AE is currently processing. "Retriving" and "Writing Output" will take longer if the sources aren't local. Otherwise the performance should be identical, as the only other thing AE has to do is to check which frame to render by looking at the file system.
- Jonas Hummelstrand