Apart from being two of the most genetically blessed young stars of the Paris fashion scene, boy-band-cute designers Olivier Rousteing and Anthony Vaccarello had something in common on their runways: Both showed tricky single-sleeve sexpot looks, the kind that literally give a cold shoulder.

Also this season, Rousteing, the relatively new designer of Balmain, found himself in step with Nicola Formichetti, creative director of Mugler. Each designer included plush white sweaters in his show. At Balmain they were tight-fitting with padded megashoulders; at Mugler they were girlie puffballs worn with black patent jeans. Vaccarello showed a fuzzy white turtleneck, too, his shown with a sexy black leather wrap skirt.

These younger designers are entering a difficult phase in their careers, when the novelty of their good looks and flashy fashion wears off and they begin to face the reality that they have to sell some of these clothes. So they try new things … like, you know, sweaters.

Vaccarello's collection was better than most, with several tough-looking coats and jackets added to his usual repertory of slinky black dresses. He dressed a short black leather wrap dress and a white satin blouse with long silver spikes and ribbons of metallic trims that looked like silver safety razors. His dresses with the single sleeves, trimmed with flesh-baring sprays of metal grommets, might have worked had he not also gone for a constructed power-suit shoulder.

Mugler's Formichetti is also in a difficult situation. Two years ago, the contemporary vision of Mugler was tailored for the social media consumer, with clothes and shows and Gaga appearances designed spontaneously, like tweets. But how do you keep that generation engaged? This show, with bubbly dove-gray cashmere hooded skirt suits and peachy fur cocoons, shapes that were based on an idealized 1960s vision of air travel, looked futuristic in an old-fashioned, 1.0 sort of way.

Rousteing's Balmain collection, an insane overdose of Michael Jackson leather shoulder pads and gold-foil harem pants, was as out of touch with reality as the customers he must hope to dress. Strange to say that the most viable items here were the long black suede stretch boots, so long they actually became pants, or poots, closing with a 6-inch zipper on the hip.

The only thing Rousteing has in common with Gareth Pugh is that Cher attended their shows. Pugh has been around long enough to know his audience, and that brings the confidence to focus on one thing well, like coats this season. Pugh included amazingly simple white topcoats trimmed with gold branches at the hems, and inky shearlings wrapped and folded in his favored triangular infanta shapes over full skirts. Some were just for fun, like enormous black coats that resembled topiary. They were made of woven garbage bags.