So for those who really want to know the list of relationship advancement and benefits, here it is. The free actions can benefit you but the drop chance? Remotely impossible, If only this really works then there'll be  no need to cry for Wrath or Bliss. By the way on Max relationship, there is "100% Drop Rate" but haven't experienced it totally. In sad reality it is really freaking hard to get those neighboring items.

Anyway here's the list for you to look forward unto, while you build relationship with your friends in "SimCity Social".

Neutral
Number of Free Actions: 5
Collectible Drop Chance: 14%

FRIEND

Buddy Towns
Number of Free Actions: 5
Collectible Drop Chance: 14%

Partners
Number of Free Actions: 6
Collectible Drop Chance: 14%
Unlock Gift Cloud Shapes

Friends
Number of Free Actions: 6
Collectible Drop Chance: 14%

Allies
Number of free action: 7
Collectible drop chance: 28%
Unlock gift Confetti Blimp

Confidants
Number of free action: 7
Collectible drop chance: 57%

BFFs
Number of free action: 8
Collectible drop chance: 71%

Sister
Number of free action: 8
Collectible drop chance: 85%

Max
Number of free action: 8
Collectible drop chance: 100%

FOE

Feuding
Number of Free Actions: 5
Collectible Drop Chance: 14%

Rivals
Number of Free Actions: 6
Collectible Drop Chance: 14%
Unlock Gift Taunt Plane

Bitter Rivals
Number of Free Actions: 6
Collectible Drop Chance: 14%

Frenemies
Number of free action: 7
Collectible drop chance: 28%
Unlock gift Alien Invasion

Enemies
Number of free action: 7
Collectible drop chance: 57%

Sworn Enemies
Number of free action: 8
Collectible drop chance: 71%

Arch Enemies
Number of free action: 8
Collectible drop chance: 85%

Max
Number of free action: 8
Collectible drop chance: 100%

TWIN
Must be friend status with city to unlock Twin City Action.
Perform Twin City Actions, then accept Twin City status when prompted.
You can have this relationship with only ONE city.

Companions
Number of Free Actions: 5
Collectible Drop Chance: 12%

Connected
Number of Free Actions: 6
Collectible Drop Chance: 12%
Unlock Gift Banner Plane

Partners
Number of Free Actions: 6
Collectible Drop Chance: 12%

Associates
Number of free action: 7
Collectible drop chance: 25%
Unlock gift Fighter Planes

Colleagues
Number of free action: 7
Collectible drop chance: 50%

Llama Fellows
Number of free action: 7
Collectible drop chance: 62%

Blood Brothers
Number of free action:
Collectible drop chance:

Twins
Number of free action: 8
Collectible drop chance: 87%

Maxed
Number of free action: 8
Collectible drop chance: 100%