I think they are supposed to be the best as they are much higher in fibre, around 23% I think, but don't seem to be as readily available as science selective or burgess, and also they don't seem to be as 'tasty' and some bunnies won't eat them. Mine are all very happy on SS and it doesn't give them any problems, so I'm planning on sticking with that for now! If you're going to give the A&P a try, make sure you get the right ones as they also do a breeder and grower pellet (and a mix) which is a totally different makeup.