A common network share(on one of the 2 systems or even a 3rd one) is about the most easy easy way to do it.
You will want the share to be password protected. You can save the credentials on the computer(or use the same on both) to make things seamless after the first connection.
Just remember by default network shares(even when mapped as a drive) do NOT have a recycle bin. When set as locations for users folders they will recycle on the local computer, but you have to be aware of this limit when deleting things over the network.