We’ve got some details below, but the quick and dirty is that Cyrano is defined by his quick verbal wit and Christian by his lack thereof. You get the picture.
There is a marked difference in the styles in which soliloquies and dialogue are written. The first uses a much more poetic language, drawing metaphors and employing rich imagery, and they tend to drag on (often longer than we wish to sit and listen to them, but that’s another point all together). Cyrano and Roxane speak in much the same way – often employing passionate poetic language. Ragueneau, who resembles Cyrano in being a poet, approaches language with quick cleverness and humor – as Cyrano sometimes does – but he does not have the depth of emotion that Cyrano’s verses convey. Ragueneau is more concerned with pumping out as many puns and allusions as he can to entertain his poet-friends.
Normal dialogue, of course, is terse and sharp, and uses a lower, more common register of speech. Christian speaks much more simply, having something of a simpler mind.
Were you awake during that first act? Everyone and their mother put in their two cents about Cyrano and his heroic, admirable qualities. While this does tell us that Cyrano is heroic and admirable, it also tells us that he’s a showboat, and that reputation is a big part of his character. The way the cadets talk about de Guiche reminds us that, in fact, he’s a total jerk, and Cyrano and Christian’s waxing on about their desire for Roxane is a hint that she’s, well, desirable.
Nationality is important in Cyrano de Bergerac; Rostand characterizes the Gascons as particularly hot-tempered, proud, and almost recklessly brave. This is presented as a national trait and gives unity to, say, a band of cadets fighting against the Spanish.
Cyrano’s nose is larger-than-life and ridiculous. So is Cyrano. Christian is hot, but that’s pretty much all he is. Need we say more?