Parking options for Toronto Pearson Airport (YYZ)

I am planning a short, five-day trip out of the country in mid-June, in which I will be departing and returning to Pearson. Since I will be returning late at night, I'll need to park at or near the airport instead of being picked up.

After a bit of research, it seems like parking right at the airport is the most reliable option, but also the most expensive at $20 per day. The alternative parking places look much cheaper but reviews for places like Park 'n Fly are mixed or negative, with many complains about having to pay too much or unfriendly attendants/shuttle drivers.

I am wondering if parking at the airport is worth the extra money, as far as paying and security go. Alternatively, if it makes more sense to park somewhere else nearby, how secure are those lots, especially later at night? Should I be worried about walking in the parking lot or the security of my vehicle?