I have seen both sides of this situation a few times, and I have to support those who emphasize creating what the band wants as a whole, what the individuals in the band want, and what you want as producer/engineer, roughly in that order.
I would not waste time considering what A&R people want, because they certainly aren't. They are concerned with what the buying public wants. If a label rep personally likes your music, that is fine, and will contribute to their support of it. But, at the end of the day, public appeal is paramount, and the only true thing that makes something appeal to the public is that the music is genuinely believed by the people who made it. After that, if the style fits someone's groove, great, you have a new customer:-)
I am often worried to see artists chasing down what they "think" labels want, while the labels are chasing down what they "think" the public wants. This is all putting the cart before the horse, and keeping the artists 2 steps removed from the public.
The artists should be leading, not following.
I am sure that some of the roughest street-sounding rap artists deeply believe their recordings are the "shit," and no one can tell them otherwise. That belief alone can often carry them to success.
Similarly, I am certain that Brittany Spears believes that her recordings are the shit, as do all her host of engineers and producers. I truly feel that their belief in their multimillion dollar stuff is no different from that of that home-recorded rap artist.
At the end of the day, only YOU (band, artists, engineer, producer) have to feel it is a masterpiece. If you do, that will show through. If you do not, it will be immediately obvious. There have been far too many recordings out there with massive commercial success that are technically horrible, to think that you need to plasticize your recordings to make them palettable to a few oversized companies.
My feeling is that recording artists (including producers and engineers) should make great art, and let the business men worry about making great business. Sometimes the rare single person can do both, but usually not.
Just my 2 cents,
-K