Pls help with applying....

[MTomislav]

Hello,
my name is Tomislav, I live in serbia. I am acepted at UBC for Master of mining engineering, with co-op internship.
I have dilemma about that how should I apply for student visa. I have two options:
1. Apply for 12 months student visa, and then from Canada before co-op internship program I will apply for extend my visa.
2. Apply for 21 months student visa (with co-op internship included). Duration of this program is 21 months.
Please help me with this choice.
Can you tell me must I apply for work permit in both cases.
What you think have I good chance for visa?

Thanks