It's really just a personal preference. There's no practical difference.
If you make the connections in the UI, you can see them all in the "Node" tab of the emitting object, while if you do it in code, you have to hunt through looking for connect
statements.
On the other hand, if you're instancing objects and making dynamic connections, or if you need to connect a lot of objects, doing it in code is going to be much easier.