My brother studies at Centennial, and he quite likes his college. Sheridan is known for its strictness. But it has a good placement record, and so does Centennial. According to him, Humber and George Brown are average colleges. He does not know much about Conestoga College.

In the end, your choice of college should depend on your course. Each one of these colleges is best known for one or the other program. You must choose accordingly.

My brother is currently pursuing the Construction Engineering Technician (T161) course from George Brown College. It is a two year course, and an extra year places it into an advanced diploma (T105). 

George Brown offers plenty of job opportunities from a variety of construction companies across Canada. The college regularly holds a job fair in which prominent companies like Bird Construction, Aecon, EllisDon, PCL, etc. take part. A large number of alumni from our college work at one or the other of these reputed companies. 

All the three colleges offer internships, but according to my brother, George Brown is a better option for the construction management program.

My friend is a graphic designer. He completed his studies in Graphic Designing from Toronto itself. According to him, Sheridan College in Oakville is the best choice for graphic designing courses, followed by George Brown College. Centennial has a dedicated school for this subject. 

Seneca and GBC offer graphic designing lectures on PC, while Centennial uses MAC for learning purposes. MAC is more popular among graphic designers because it offers a smoother experience for many design softwares. Even if such softwares have a PC version, they require less keystrokes/steps to complete a task on MAC.

The infrastructure of Centennial is top class. I know this because I have studied in that college. Centennial offers some really good Engineering and IT courses. Both the colleges are at par for Arts. The location of Seneca, the North York region, is rapidly growing. This makes Seneca a better option for Management courses because of its rich networking opportunities. 

Both the colleges have their own strengths and weaknesses, and none of them is better or worse than the other.