I prefer back locks, especially mid backlocks as they are strong, reliable, and ambidextrous. They also have a bias to close making them safer to carry without a sheath. I like the axis lock as a second choice but I have seen them come open in purses and pockets. I do not normally care for liner locks (fail locks we used to call them on the ranch) as they do not hold up well under hard use. The same can be said for frame locks. They are fine for pocket knives, but they tend to want to be open and only stay closed by a detent that is usually not strong enough.