I'm from Hong Kong, thinking to immigrate to UK or Canada with my teenage son, which country is better?

You're about to receive biast answers from people living in both countries. You should do some research first. Canada has a better education system. Think about what kind of life you want and compare. The UK is going through somewhat of a job crisis. Canada is much bigger but that isn't always important. Both have great healthcare. Being a Canadian I would recommend Canada but make sure you find what's right for you. Maybe compare houses, jobs, ETC

before you start picking where YOU want to live, how about you tell us under what premise you plan on getting the correct visas to allow you into these countries.

If you want to live with nicer people, I think Canada would be the better choice.

You don't state any qualifications which might enable you to apply for immigration to any country, or even qualify for a temporary employment visa if you could ever find an employer to hire you & apply for your visa. There are no jobs for you in either UK or Canada. Unemployment rates in UK, almost all EU countries, US, and many, many more are higher than they were during the Great Depression of the 1930's.

So even if you qualify to apply to either one, and eventually obtain an immigration visa, there are no jobs for you.

Your son would probably like Western Canada better. Lots to see and do. Wide open spaces, fishing swimming, ice skating, soccer, hockey, beaches and because you know English, you would do well. Check out the visas you can get.
UK might be more difficult since they are a member of the European Union and Asians aren't part of that.

I'd say Canada only because of hockey.

To quote a show you wouldn't have seen 'I want to moonwalk son but lifes a shithouse'. You don't just pick a western country to move to, I can't speak for canada but your chances of getting the correct visa for the UK are between slim and none thanks to the other trillions of asians and eastern europeans who flooded here en masse leading to immigration being tightened.

I think that you may have difficulties getting a visa for the U.K.as there are millions of unemployed people at present and only professionals are needed

more chance of getting into Canada

http://www.cic.gc.ca/english/index-can.asp

As an Englishman I would say Canada. Apart from their draconian anti smoking laws it's a wonderful country.