Your first source states in the headline that the drone strikes "kill innocents 90% of the time".

Then, in the body, it says the drone strikes "caused the deaths of unintended targets nearly nine out of ten times".

An unintended target is not the same as an innocent, and it's misleading to use them interchangeably.

Your second source is better, but you haven't provided any data on the civilian-to-target ratio of more conventional methods. You can't have a meaningful comparison without that.