Through the vagaries of scheduling, the Kennedy Center has recently played host to both the New York City Ballet and American Ballet Theater for three weeks apiece, and the engagements were only separated by a single week. This circumstance afforded Washingtonians the hitherto rare opportunity of seeing the nation's two major classical ballet troupes virtually one on top of the other, and of making inevitable -- and instructive -- comparisons between them.

There is no question here, of course, of deciding which is "better." From a global standpoint, the two troupes rank with Russia's Bolshoi and Kirov Ballets, England's Royal Ballet and the Royal Danish Ballet as the topmost echelon of the international realm. In the United States today, no other companies can be placed beside the New York City Ballet and ABT in terms of either sheer size or artistic substance.

But the two are at opposite poles in their approach to the art and business of dancing. People have personal preferences for one or the other, naturally, but the issue of superiority is specious.The contrasts between them, however, are illuminating -- they pinpoint the esthetic and economic dilemmas characteristic of ballet with a big "B" in today's world, as well as various options for coping with them.

The two companies have several things in common. Both are large organizations, though the New York City Ballet has a palpable edge in numbers --these figures to the Bolshoi complement in excess of 150).Despite their dependence on methods and works rooted in foreign traditions, both are recognizably "American," in some not too narrowly definable sense.

And both totter on the brink of financial disaster -- the New York City Ballet barely weathered a crippling musicians strike just prior to their Kennedy Center visit, and ABT, chronically ailing in this respect, still bears the scars of its contract struggle with the dancers' union last winter. How the two of them will make it through the '70s without massive new sources of funds no one quite seems to know.

In most other ways, the two companies diverge widely. The New York City Ballet has a grand theater it can call its own -- the New York State Theater at Lincoln Center -- and hardly tours at all, playing outside of New York these days only at Saratoga in the summertime and in Washington. ABT has no such home base, though it has vainly sought one since its founding, and this year will present major seasons at the Metropolitan Opera in still another attempt at sinking roots. Though the company has succesfully extricated itself from its former whistle-stop existence, ABT still makes lengthy, cross-country tours.

The most conspicuous difference is one of artistic policy, but it's also a consequence of the accidents of personality. The New York City Ballet has George Balanchine, the century's most gifted and productive choreographer. ABT does not -- it's as simple as that. As a result, the New York City Ballet revolves around the creativity of its artistic director, where ABT is focused upon the glamor of its international stars and the breadth of its repertoire.

The New York City Ballet has as strong an entourage of dancers as any company in the world, but its character as a troupe is defined by the fact that it is an emanation or extension of Balanchine. The dancers have a look and a way of moving that Balanchine has given them, and though they do ballets by other choreographers as well, they always retain their own clear stylistic identity.

Though co-director Lucia Chase rules over ABT with undaunted authority, this company mirrors the image of no single individual. Its eclectic repertoire requires instant stylistic adaptability -- the capacity to shift from Petipa to Jerome Robbins to Antony Tudor to Agnes de Mille to Fokine, and so on, without pausing for breath.

The dancers inevitably tend to fall into a kind of platoon system, geared to their particular sensibilities and inclinations, but there are also constant attempts to break these ranks -- to assign a classically oriented dancer, most comfortable in "Swan Lake," say, to the vernacular of de Mille or the psychological involutions of Tudor, and vice-versa.

These differences have their reflections in the expectations of an audience. With an ABT performance, a change of casting is apt to cause cataclysmic dismay or jubilation. In the cast of the New York City Ballet, a substitution in programming is more likely to bring on such reactions than a switch of dancers. The same differences are mirrored in our memories of a given season -- it's the ballets we recall from the New York City Ballet visits, but specific performances by individual dancers in the wake of an ABT engagement.

So it was with the recent appearances. It's "Union Jack" we recall from the New York City Ballet run, and "Four Temperaments" and "La Valse" and "The Concert" and "Symphony in Three Movements" and "A Midsummer Night's Dream," and so on. What sticks from ABT, however, is Carla Fracci's "Giselle" and Gelsey Kirkland's "The Leaves are Fading" and Erik Bruhn's Madge in "La Sylphide," as a few examples.

Of course, it's easy enough to cite exceptions -- "Les Noces," for example, the Robbins-Stravinsky masterpiece in the ABT repertoire whose choreography overshadows the personalities of its executants. But that's what makes a rule a rule. The fact is, ABT and the New York City Ballet are antipodal species of dance companies. What's terrific is that we don't have to give up either one of them.