Is there any real difference between using growbags and pots of compost for
growing tomatoes in?

I intend, when I can get my lazy bottom off this chair, to plant some
tomatoes in the greenhouse, but when I go to the garden centres they have
both compost bags, and growbags, and I wonder whether there is any real
difference between the two, or I could use the compost from my heap.

SWMBO tells me that when growing tomatoes in growbags you must feed them.

Alan