One of the reasons working dogs and show dogs have generally separated into two very different breeds is that it is almost impossible to breed "top of the line" performers in two arenas at once, and that is especially true for a slow-breeder (any large mammal) and one that has a small gene pool (all show dogs).
JBS Haldane pointed this out about 50 years ago when he was writing about "substitution costs" faced by breeders. This is now known as "Haldane's Dilemma."
Haldane, along with Sewall Wright (of COI or Wright's Coefficient of Inbreedining fame) and Ronald Fischer more or less created the math we still use to today when looking at population genetics.
Yes, you can try to "shoot for the middle" in terms of two or more characteristics, but the results, for the most part, will not be top-of-the-line in either arena unless you are selecting for hundreds, or even thousands of years, which no one has done in the world of dogs.
It should be said that Haldane may have inflated the true cost of substitution -- a point he made himself. Nonetheless, there is very little doubt that a cost is there, and it is large and is most easily addressed by either having massive amounts of time, or really large populations, or very rapid breeding (as in mice and rats), none of which we have in the world of show dogs.
For a related post, see Islands of Wolves, Rats, Lions and Dogs.
By the way, today is JBS Haldane's birthday -- born November 5, 1892.