The advantage is that it will create a constant current in the canal.
Regardless of the length of the canal -- at least until evaporation becomes a factor.
The constant current can be leveraged to move boats, presumably fairly deep hulled so the really get in the way of the current, and said boats can carry whatever.
Two canals adjoining allows the boat to be moved from one to the other, and sent back to the other end, ad infinitum.
When you put a cork in a river, it'll go from the mountains to the sea, because the current carries it.
What I'm suggesting is create an artificial current using pumps. The two 'c's run in different directions, so you have a full transport loop.
All four ends are physically adjacent, so you only need one pumping station if you connect the two c's across one end.
Old time canals used donkeys and engines to navigate. This works like a river and a raft. You float to where you're going.