These types of proprietary rewards schemes (e.g., CIBC Avenutra, RBC Avion, MBNA Rewards) are a double edged sword in that redemption will almost always be better than Aeroplan's meagre offerings to non SEs given that you are using the proprietary points to basically buy cash tickets, but the challenge is that your only avenue for generating points becomes one or two credit cards.

So for someone with a fairly substantial spend (or modest travel goals), something like Aventura could make sense. I know a guy with a body shop who puts through hundreds of thousands of dollars in car parts a year on his Aventura, so it's a good proposition for him. But for anyone else, it could take a long time to amass enough points to do what you really want to do.

I haven't applied for an Aventura since CIBC stopped the 1:1 Aeroplan conversion a few years ago, but as I recall it was a fairly simple process, not really any different or harder to get than Aerogold.