ADA Aqua soil seems to be the easiest and simplest.
However, there are other factors, eg the user.
Aestehtics if you want a white sand look etc, or like a certain grain size or color.
I personally really hate layered sediments with sand, soil, gravel mixtures.
So I rarely do layered systems for my aqauriums.
I use the soil + sand caps almost exclusively for lab test however.
But I'm not gardening there..........