Eco is far more broad and at the end of the day, is a philosophy. It requires a bit more independent thought and also helps if you have an interest in the topics. If you're an avid consumer and want to know more about how things like interest rates, globalisation, protection, etc.. affect you, it's a great subject. I found it very interesting. You also need to stay up to date on economic news and know some statistics in your exams to do well. It may help you a bit with university since it gives you a background to economics (which is a core subject in Commerce) but the HSC version is more definitions based whereas university is far more statistics/numbers/graphs based.
Business is a traditional rote learn subject. You learn a bunch of definitions and case studies for the most part and regurgitate them in an essay or exam. It's enjoyable but one of those subjects where it's easy to do ok, but difficult to do really well. It's more about essays and is a bit waffly. That being said you touch on many issues which are relevant to small business owners (e.g. if you want to be an entrepreneur) and in terms of practicality for the real world, the stuff you *touch on* on this subject (e.g. balance sheets, ratios, etc) is very applicable to a lot of Commerce jobs.