Chathta hoon vs chahiye

There are two ways to express want in hindi as far as I can see: main chahta hoon, मैं चाहता हूँ; mujhe chahiye मुझे चाहिये.

in what contexts are both used?

I think chahiye is stronger and expresses need e.g. As in ham bhooke hain aur hamko khanna chahiye हम भूके हैं और हम्हे खन्ना चाहियें. we are starving and we need food. And the other expresses a wish Main Canada jaana chahta hoon e.g.  मैं कनाडा जाना  चाहता हूँ

Hi,
I agree with you. 

मैं चाहता हूँ;  - I wish to have...
मुझे चाहिये – I need..

Also  "We are starving and we need food"  in Hindi is 

हम भूखे ( NOT भूके)  हैं  और हमें  (NOT हम्हे) खाना ( NOT खन्ना)  चाहियें।

 Also I agree with you   "I wish to go to Canada" in Hindi is

मैं कनाडा जाना  चाहता हूँ  ।

Thanks
Sudhanshu