Only thing with the free samples is that they are barely a meal. I've had them to see what the kibble is like.

I suggest deciding which manufacturer you like and buying one of their smaller packs [2.5, 3.0, 4.0 KG] rather than the 15 KG. Skinners, Burns, Wagg do them. That way you won't buy a 15 kg and then discover they don't like it.