I like the all in one convenience of AS. But I like used AS even more; all the convenience of fresh AS but without the massive nutrient load at start up. For many, especially beginners,
Amazonia Light might be a better option since it's not quite so high in nutrients.
However, you'll get no argument from me regarding the use of
soil or compost. I think if you can get your head around the counter intuitive idea of putting actual soil in an aquarium then it's a no brainer. Soil is dirt cheap (that gag never gets old), and since it's the stuff that plants usually grow in, it's great for growing plants. I've never had healthier Crypts and swords etc, than when grown in compost capped with gravel or sand.
However, just one word of caution, good garden soil doesn't necessarily make good aquarium sediment. Often it's the least toxic that's the most suitable. That's why I prefer branded compost, it's usually been tried and tested as aquatic plant sediment and is universally homogenous so you know what you're getting every time.
On the subject of Eco Complete I've never used it, but from what I've seen and read it's
pretty much inert with no intrinsic nutrient content. And I don't find it aesthetically appealing either; it looks and feels unnatural. In effect it's kind of like paying Gucci prices for plain old gravel, which doesn't make sense to me. However, if it works for you and you're happy with it that's all that matters
🙂