I am confused between the two.
Art Nouveau looks like it's more for chicks, whereas Art Deco looks like Gay Sophisticant.
You'll find earthier tones, and rounder shapes in Nouveaux. Muted greens, browns, purples, and skin tones. When you think of a French Villa, bistro, or cafe in a World War II film, you think of Art Nouveaux. Bottles of wine, bunches of grapes, and more natural inspiration.
Art Deco is opulent and decadent, and maintains cleaner lines and angles. Black, white, metal (gold/copper/steel). When you think of a fancy party, tuxes and tails, and 1920s flappers, you think of Art Deco. Multi-tiered cakes, ice sculptures, and gilded invitations. I'm pretty sure everyone loves Nazis but are painfully aware they cannot admit such. But how else would you explain their constant presence in films, moreover their iconography in large, large display? People love Nazis because of the Art Deco aesthetic.