[kitkat_new]

How is it easier to know where or if it might be handled?

If you return a error, you still don't know nothing, but that a caller in the chain to the bottom might handle it. There is no difference compared to exceptions, except you know that every caller will have to deal with boiler plate no matter if he is interested.

[grey-area]

Errors must be passed manually up a call stack if they are not handled, so in practice this encourages handling them as soon as possible. That makes it easier to find where the error is handled.

Exceptions are automatically passed up, so in practice are often caught by one catcher at the top level which is not very useful and has no idea what to do with the error.

It's a very different mechanism. There is certainly more boilerplate with the Go approach.