Neural Networks or Human-computer interaction

The worthiness depends on three factors:

• How familiar are you with the topic already?
• How good is the course/class you want to take?
• What are your interested in more?

Especially for HCI, there is a broad range of "common sense" information you would also easily obtain from reading a good book or a wider range of articles about it also published on the internet. On the other hand, there indeed exist many deeper insights mostly obtained by Psychology studies. If the course is done right, you can indeed learn a lot about the topic and the real considerations to use for developing an interface.

For Neural Networks, one has to say that this is a typical hype topic. It would be mainly interesting in what application domain the course wants to deal with neural networks. You can be quite sure that you won't program or use any neural networks for web development. On the other hand, if the course is done right, this could be a good opportunity for you to broaden your knowledge. Especially, deepening your understanding about the theory of computer science. This highly depends on how the course is laid out, though.

HCI is a topic which helps your career as a web developer, but only if you feel incompetent in that topic (then it is a must) or it is done very well. Neural Networks is a topic which has more potential of being really interesting hardcore computer science stuff, where you indeed learn a better understanding about something. If you are interested in NN, you should not pass the opportunity to get an education which is not narrowly concentrated on the domain of web development -- and, after all, perhaps find more interest in other stuff (it is always good to know other directions you would perhaps like to go into for the future).

Neural networks sound cool until you read the fine print:

In modern software implementations of artificial neural networks the approach inspired by biology has more or less been abandoned for a more practical approach based on statistics and signal processing.

This is something that has mystified me for years. Here you have an amazingly complex and powerful control system (real-world biological neural networks), and an academic discipline that appears to be about modeling these systems in software but that has in reality abandoned that activity.

If you're doing web development, your time is probably better spent in the HCI course.

Go with what interests you the most. The HCI stuff will be much easier to pick up later as needed, you'll likely never get another chance to learn about neural networks!

For prospective employers (at least the good ones!) you need to show a passion and excitement about what you do. I'd sooner hire someone who can enthusiastically talk about neural networks than someone who has an extra credit in HCI.