Both. Alternate them. How would you feel if you would need to eat always the same?
This is why they don't eat also the Fidaar. They will, just they need also some different.
Note also, only giving dry food to cats is cruel. Give them regularly, ideally every day, some other, too (ideally, raw flesh or fish, but never raw pork).
If costs matter you, you can use anything and any organ. They eat their pray in the wild as it is.
The like bloody hearth at most, and also lungs. Better if it is as it came from the butcher, without washing, because the odor of the blood excites them.