title_body: Advantages to having more rotors? I have a quadcopter drone, is there an advantage say of having a octocopter instead of a quadcopter. Will it improve performance?
upvoted_answer: Performance is unlikely to be improved, in terms of speed or agility, or even load-bearing capacity, as they are heavier, slightly less efficient aerodynamically, and more expensive.
  
  What you do get is a degree of fault-tolerance. 
  
  With a quadcopter, losing one rotor means your drone will fall out of the sky. With an octocopter (or hexacopter, but an octocopter can lose more motors and still be able to fly) losing one rotor is not fatal - it will still fly, however, it will have a reduced control authority.
  
  This makes them very desirable for carrying expensive loads - such as a £50,000 camera - you really don't want to drop that out of the sky if you have a fault.