[Sniper]

This bit of info also seems important...

Benefits
By joining an alliance you will find that your statistics are given a boost based on the average statistics from all members in your alliance. For instance, if you have a level 5 strength as well as the rest of the members in your alliance, you may have a better chance of successfully attacking a base with a level 5 defense than you normally would. The same thing applies with fortification, stealth, and security. However if you have a level 9 strength and the rest of the members in your alliance are all level 10 you may be hurting the alliance more than helping them. This is important to remember if you are the owner of your alliance and have the power to discharge members.