Hello! As a person who studied in Centennial and have friends who studied in two other colleges, I can tell you that the only difference is a) college location and b) whom you want to study with. Everything else is pretty much the same.
If you want to study with mainly people from India, go to Centennial, China and other Asian countries - Seneca, a little bit of everyone including many Canadians - go to George Brown. This is the best advice I can give you. I don't know much about Humber. Think with whom you'll be more comfortable as your co-students. I know that some people feel more comfortable with the majority of classmates being from similar culture as them, others come to Canada because they want to escape it and be open to more opportunities. I'd choose George Brown because it's more diverse, because it's downtown in a very beautiful area and because it has co-op. Co-op programs are very important. They can help you stay at the employer where you passed co-op or find another work in Canada.
Another piece of advice. Choose two year program and get a three year post-grad work permit. One year is not enough. If you want more details, I can share my personal story and many stories of the people around me. You will work but you will not be able to stay with one year work permit. Play safe!
As for employment, everybody in Canada is looking for a Canadian experience. Employers don't care about your previous experience at home. It's good that you have it but not enough. Co-op will help you get that Canadian work experience.
These is my advice learnt in a very hard way. I wish somebody told me what I'm telling you right now before I came to Canada.
