In the case of an espresso blend, what constitutes "more complete and pleasing" is obviously relative: relative to the palate of the blender, to the expectations of the consumer, and to the traditions to which both blender and consumer refer.
At this point it might be useful to refer to the array of tasting terms listed earlier: acidity, body, aroma, finish, sweetness, bitterness, and so on.
It would be safe to say that all espresso blends everywhere aspire to as full a body as possible, as much sweet sensation as possible, and as much aroma and as long and resonant a finish as possible. The differences arise with acidity and with the bitter side of the bittersweet taste equation.
Most northern Italian roasters present blends with almost no acidy notes whatsoever, whereas North American espresso blends often maintain some of the dry, acidy undertones most Americans and Canadians are accustomed to in their lighter-roasted coffees. This difference is simply a matter of choice and tradition. North Americans are used to acidy, high-grown Latin America coffees, and Italians are accustomed to drinking either Africa robustas or lower-altitude Brazil arabicas.
My own position, for what it’s worth, is that acidy notes need to be felt but not tasted in espresso blends. They should be barely discernible, yet vibrating in the heart of the blend.
Recall that acidity, or dryness, is a property of the bean that diminishes as the roast becomes darker, to eventually be replaced entirely by the bittersweet, pungent flavor notes characteristic of dark roasts. The value of the bitter side of the bittersweet equation is also an issue in blending philosophy, with Italian and Italian-style roasters coming down more on the sweet side, and North American roasters more on the bittersweet. As I pointed out in discussing style of roast, this difference is reflected in the somewhat lighter roasts preferred by Italian roasters, opposed to the darker styles favored by most North American roasters.
So, on both accounts, blending philosophy and style of roast, northern Italians put a premium on sweetness and smoothness and North Americans on punch.
It is clear why North Americans might prefer a punchier, more pungent and more acidy espresso coffee: They need the power of such flavor notes to carry through all of the milk they tend to add to their "lattes" and cappuccinos. Italians generally take their espresso undiluted and so might logically prefer a smoother, sweeter blend. But such an explanation may be entirely too rational. After all, those purist Italians also tend to dump large quantities of sugar into their smooth, sweet espresso blends. Probably taste in espresso blends is simply another irrationality of culture and tradition.