I have to say I have used both and the liver cakes knocks the treats into a cocked hat
What I also do with the liver cake is make my own treats.
Once the cake is baked - cut it into very small treat sized pieces and return to the baking tray and the oven. Turn the heat down really low - gas mark one or lower and leave until they have gone hard and crisp. They lasy forever - well almost, in an airtight container and the dogs love 'em.
I make a huge batch at a time and freeze the softer cake and store the hard treats in a tin. I don't have to make it very oftne this way so don't have the family complaining of the smell!!