What is faster for file transfers?


I have a MacPro 3,1 tower. I want to use it as a file server including its Optical disk drives for a new Mac. I could somehow:
1. Transfer via a wired network via a router connection.
2. Get a USB C to firewire adapter to set up theMacPro in Target disk mode.
3. Any other ideas?

So which is the fastest and most reliable?