MBNA Smart Cash Word vs. Aeroplan Credit Card?

I currently put $1500-2000/month on my MBNA Smart Cash World card, but seeing how I find myself shopping more at Costco, and no longer own a car, the 3% cashback for gas/groceries doesn't seem like a big deal anymore.

My friend was telling me how he's received many free trips using his Aeroplan points (which puts my 2-3x/year $50 cashback cheques seem sad in comparison), so I'm wondering if I should switch.

If so, what are my best options?

Thanks!