Really depends on your circumstances, and how you want to use the points... Do you want business or first class tickets? Do you want economy class tickets during peak season? Do you have any airline status? What is your spend comprised of, do you qualify for the points accelerators (Standard Infinite Avion is 1.25 points per dollar spent on travel)?
Amex gold is my primary card. With 2 points per dollar on travel, gas and groceries it has earned me about 750k miles since I got the card back in late 2013. 1:1 transfer to aeroplan plus my SE100K status with Air Canada renders those points incredibly valuable.
I have the Infinite Avion also, which I've also done quite well with thanks to the BA transfer which used to be 1.5:1. I've redeemed one trip with the Avios. A first class one way ticket on Cathay Pacific from Vancouver to Bangkok for 150,000 Avios. That was a nice experience, but boy is that a lot of points compared to a similar redemption on Aeroplan.