I have used both of those powder pre-mixes for Gracie - I use organic chicken thighs or turkey thighs as the base. The Better in the Raw product uses beef liver as the liver source, which I don't care for all that much. It is very smelly and since it is not organic I worry a little about contamination. (Most feedlot cattle are not treated all that well, and of course the liver does all the filtering of toxins...) The Feline Instincts product uses chicken liver, which I like better. I would be happier if more of the premix ingredients were organic.
Gracie likes them all, and I find them easy to work with. Up until recently I didn't have the time or the inclination to really get into the science of 'frankenprey' feeding, i.e. measuring out correct quantities of different sorts of meats and organs, weighing bone or adding bone meal or calcium, extra taurine as needed, etc. If it really seems necessary I would be willing to study up on it, but for now I do like the mixes because I can be assured that Gracie's raw meals are nutritionally complete.