Cygnus Knights

They can wear both, but here are the items exclusive to Cygnus.

From StrategyWiki, the free strategy guide and walkthrough wiki.

Knights of Cygnus can use the same class equips as normal players. A symbol below the character guild and name will symbolize the player's position as a Cygnus Knight.

Noblesse equipment
New Noblesse characters starting in ereb will receive:

• Noblesse Elegant Hat. Require level: 1. Weapon Defense: 3. Not trade-able.
  
• Noblesse Gorgeous Robe. Required level: 0. Weapon Defense: 5. Not trade-able.
  
• Noblesse Medal. Required level: 0. Not trade-able, not sell-able.
  

Medals
You can acquire improved medals after achieving higher levels.

• Training Knight Medal. Required level: 10, +50 HP, +50 MP. Not trade-able, not sell-able.
  
• Official Knight Medal. Required level: 30, +100 HP, +100 MP. Not trade-able, not sell-able.
  
• Advanced Knight Medal. Required level: 70, +150 HP, +150 MP, +1 STR, +1 DEX, +1 INT, +1 LUK. Not trade-able, not sell-able.
  
• Captain Knight Medal. Required level: 120, +200 HP, +200 MP, +2 STR, +2 DEX, +2 INT, +2 LUK. Not trade-able, not sell-able.
  

From StrategyWiki, the free strategy guide and walkthrough wiki.