I use eco complete. It is a high CEC substrate (meaning it holds nutrients very well). It never needs to be replaced. It is basically crushed lava rock with a few additives of other types.
The downside to it is that if you have to adjust your plants while the tank is filled, it is almost as annoying as gravel - except that it's generally lighter than gravel, so it's even more annoying.
If I use Eco Complete again, I will cap it with sand to make planting a little easier - but it's way better than sand alone.
Organic soils are good, they need a cap as well to keep the water from clouding up. They generally cause a huge ammonia spike at the beginning, so hardy plants and NO FISH while cycling.
Flourite, I believe, breaks down over time if I remember correctly, but I have not used it.
My next tank will either use eco complete with a sand cap, or soil with a sand cap.
I blame spelling mistakes on my iPad. You should too!