Comfort:
* The sofa was as soft as a cloud.
* The sofa was like a warm hug on a cold day.
Appearance:
* The antique sofa was like a stately throne.
* The modern sofa was as sleek and stylish as a sports car.
Function:
* The sofa was the anchor of the living room, like a ship in the middle of the ocean.
* The sofa was as inviting as a beacon in the storm.
Ultimately, the best simile depends on the context and the specific qualities of the sofa you want to highlight.