I felt the tick key presented less of a chance for a "faulty removal" i.e. it almost always removed the tick completely. Where with tweezers I think there is more of a chance doing something like removing the body but not the head or squeezing the tick into you more.
Better then both methods was a friends fingernails, One tick refused to come out with the key or tweezers, I began to freak out slightly, she just walked over and plucked it right off with her finger nails, the whole kit and caboodle. I think it is a talent not every one possesses.
As she walked away she just looked back at me like "you big baby"