I apologize for mistaking you. I thought that paragraph was, not the narrator telling the audience what Bingley's party thought during the Ball, but the narrator telling the audience how the Bingley party spoke of the Meryton Ball afterwards. After all, it starts:

The manner in which they spoke of the Meryton assembly was sufficiently characteristic.

I took the rest of it to encapsulate what was said.

Bingley had never met with pleasanter people or prettier girls in his life; everybody had been most kind and attentive to him; there had been no formality, no stiffness; he had soon felt acquainted with all the room; and as to Miss Bennet, he could not conceive an angel more beautiful. Darcy, on the contrary, had seen a collection of people in whom there was little beauty and no fashion, for none of whom he had felt the smallest interest, and from none received either attention or pleasure. Miss Bennet he acknowledged to be pretty, but she smiled too much.

Even the wording after the first sentence conveys that impression to me: Bingley would speak in over-the-top compliments, listing good points in rapid succession, and praising Miss Bennet in broad appreciation. Darcy would speak more formally, dismissively, and would barely acknowledge Miss Bennet's beauty to be 'pretty,' without adding a caveat.