In retrospect, based on everything I now know, it should have been an easy choice. But I spent quite a lot of time reading, reviewing & debating. In case it helps you, here are some of the items I considered at the time.
- According to Wolfram|Alpha, there are approximately 1 billion people who speak Mandarin, of which nearly 900m speak it as their first language. Cantonese, on the other hand, is spoken by 55m people. Mandarin is by far the number 1 language in terms of the number of native speakers, and that's a good reason to speak it.
- And of the 55m who speak Cantonese, a large proportion also speak English. For Mandarin, this is not the case - so in terms of actually needing to speak Chinese, Mandarin is the clear choice.
- Mandarin has 4 tones (plus neutral), which is difficult enough for Westerners to grasp. Cantonese has 9 tones (plus neutral), which definitely makes it more difficult topick up.
- Even in Hong Kong, where Cantonese is the main language, in recent years it has been Mandarin that is now compulsorily taught (especially at international schools), and not Cantonese as I would have thought.
- Most of the material on the web for learning Chinese is Mandarin-based. It's not impossible to find Cantonese material, but the choice is certainly much more limited.
The main reasons I would have chosen Cantonese were:
- I was visiting Hong Kong quite often, and Cantonese is the main Chinese language spoken there.
- Chinese restaurants generally seem to have Cantonese-speaking staff. Of course I'm generalising, but when I eat Chinese - in London, New York, Munich, Zurich, Johannesburg - they don't always speak Mandarin, just Cantonese.
Life's never simple, and so even choosing Mandarin isn't enough - because there are many dialects which exist too. The most commonly-taught version is Standard Mandarin, known as Pǔtōnghuà [普通话]. And the good news is that most of the Mandarin course material on the Net seems to focus on this Standard Mandarin. Other variations include Guóyǔ [国语] which is spoken in Taiwan and is actually quite similar, Shangainese, Beijing dialect, and others.
Here are some additional links which might be of interest:
And if you have a different opinion to mine, let me know in the comments.