@joerob40 I would say that can be tweaked a bit if someone has fluctuation in their work and earnings.
If they're in a trade that has boom and bust cycles, and for the tax year being considered they just did a ton of hours and had lots of income, then it's easy: RRSP.
That nets the nice income tax reduction, which is precious.
If someone had a slow year and their income is already low and in a low tax bracket, using making the RRSP claim might be squandering something that could be better used some other time.
I would say that that when it's a toss up, RRSP is favored because it reduces your income tax payable. That's "free" money from the government. You don't get that every day.