Hi both have good CEC. I heard good things about Stratum but what i dislike about it : it does not hold forever. It becomes a kind of mud after a couple of years that i heard. Maybe people who used it can confirm or not.
Eco-Complete, Flourite, have good CEC, last for life. However true they do not have nutrients, or very few. You may have to fertilize. This is what i do, i have Red Flourite and fertilize in the water column.