Most people don't like the MG soil with the pellets because it's time-release and it's impossible to control what your plants are eating at each stage of growth. If the ferts are 15-30-15, having that much N around will also slow maturation and cost you bud in the end. So even if they look really green and healthy until the day you harvest, your plants aren't producing as much as they could and on top of that the weed will be harsh and not burn properly since you can't flush properly before harvest.
It might be useful for outdoor grows, but I know it's not going anywhere near my plants.
The 'organic' potting mix doesn't have the pellets. I used some i had gotten for the backyard for some clones once and it was the worst thing i've grown weed in and came complete with a spider mite infestation. If you do use the stuff, cut it down with perlite (it's very thick!) and start adding nutes early.
Coco and liquid nutes are better and cheaper in the end since you can reuse the coco and only have to restock on ferts.