4 Waterloo co-op terms would spread out over a course of 2-3 years. So the tax rate you fall under would differ from that of a full 16-month PEY because you may be making less money over the course of the same year.
Yes, that was my point. By spreading out the income over a longer period, you pay less in taxes and thus have more take-home pay. Helps a lot with paying tuition/loans off.