Lamb liver is my liver of the moment. I was eating mostly chicken liver since it has about the same nutrients but less vitamin A (55,000IU versus 123,000IU) allowing me to eat more liver!, but I switched to lamb, slightly less frequently than once a week, in order to get the copper (35mg per 500g versus 2.5mg for chicken).
For taste, it's certainly closer to beef liver than chicken liver maybe slightly 'meatier' than beef. I've not had calf liver. I think chicken liver is infinitely preferable for pate, I can't even imagine how people turn lamb liver into a pate but apparently, some do. I also prefer my lamb liver more well done than my chicken liver, but am aware that this is a terrible offence in many people's eyes.
I eat lamb liver two or three times a week - I love it. I fry some onions in butter / lard until soft and going golden then add the thinly sliced liver for two or three minutes, salt and pepper and serve.
Using exactly the same process and adding a teaspoon of carraway seeds and a teaspoon of sweet smoked paprika to the onions before the liver goes in, and adding sour cream just before serving it, makes a very delicious meal.
Lamb liver tastes and smells like urine. Straight up. I too, have heard about the wonders of grass fed liver so I gave it a shot last night. So gross. I had to throw all of it away.
Granted, I'm no chef. But stil--no matter what I did (soaking it acid water before hand, cooking it lightly, cooking the hell out of it), it smelled like pee.
All these hip paleo people are just downing liver like it's actually good or something, so either they know something I don't know about cooking liver, or they like (or don't mind) tasting urine. I suspect it's the former.