It really depends on what you want to do, and on how many university applications you have in your budget. I know that when I initially applied, the cost of the application covered applying to 3 different programs – so I applied to one each, at U of T, Ryerson, and York. A year later, when I applied again, it was a different system because I was no longer in high school: my application fee covered 5 schools, and unlimited programs at each, so I took advantage and applied to 3 different undergrad programs at Ryerson (journalism, English, and ACS) and other programs at 4 colleges.
This stuff is really confusing and there’s lots of rules, so I would highly encourage you to talk to your guidance counsellor. (If you happen to be a Rosedale student, try to get Ms. Backay. She’s the best.)
I applied to multiple programs at Ryerson because a) it didn’t cost me extra and b) I could actually see myself potentially enjoying taking an English degree, if I didn’t get into journalism. But if you know that you’d only really want to take one kind of degree, then you might not want to bother applying to others, especially if it costs extra.