There is a definite difference between clothing choices for casual occasions and clothing choices for dressier occasions. I will define some choices in comparing casual vs. dressier clothing.
For example, a sweater (single layer) vs. a sweater set (double layer) means that the choice on the left is more casual than the choice on the right.
1 .Application of layers: Single layer; 2 + layers (sweater vs. sweater set)
2. Feel of fabric: Textured; smooth (tweed vs. satin). Tweed is more casual than satin.
3. Details; no tie or scarf: Ties and scarves dress up clothing.
4. Outer details; heavy outer stitching: No outer stitching (denim vs. silk)
5. Matched separates; unmatched: Matched (blazer and slacks vs. suit)
6. Jewelry; rustic: Refined (ethnic, large accessories, leather, wood vs. fine metals, gold, pearls, gemstones)
7. Soles of shoes: Thick soles; thin soles (wingtips vs. sneakers)
8. Accessories: more;less (Simplicity can be more elegant)
9. Fabric of shoes: Textured; smooth (cork vs. patent)
10. Men's shoes: Penny loafers (excluding sneakers); wingtips (formal)
11. Women's shoes: Heavy; light (heavy voots vs. high strappy sandals)
12. Fit of clothing: Unstructured; structured (sweatshirt vs. suit)
13. Men's shirts: Plain cuffs; French cuffs (buttons vs. cufflinks)
14. Collars: No collars vs. collars
15. Colors: Light bright colors; high dark contrast (pale pink vs. electric blue)
16. Appearance: Casual, relaxed, friendly; formal, stable, credible, business-like (jeans vs. blazer)
17. Lines: Curved; straight (Peter Pan collars vs. angled collars)
18. Fabric design: Prints; solids (paisley vs. solid silk)
19. Industry related: Blue-collared industry; corporate industry (jeans vs. suits)
20. Vests: Vests; no vests (vests will dress up a blazer or suit).