I've never used MTS so I can't comment on that. However the Miracle Grow option is less work for you, in that you can pick it up anytime of the year at many places and use it immediately, as opposed to having to wait to make it.
Since you are setting up a couple of tanks why not try a couple different strategies.
Do one with soil base and cap it with Eco-complete. Then do another either soil base with a sand cap or straight sand with root tabs for the individual plants.
That way you get to see what YOU like better.
It was impossible to get a conversation going, everybody was talking too much.