As per my understanding, the duration of one's post-graduation work permit depends on the length of the program and not on the total amount of studies. You are required to apply for your PGWP no later than 90 days after completing your program. If your program is officially 8-month long, you get an 8-month long PGWP; if it's officially 1 academic year long (still 8 months), you get a 1 year long PGWP.
So, I believe you can apply within 90 days of completing either program but your PGWP will still be either 8 months or 1 year long. Also, you'll get the work permit only once.