I use the foot spikes and have had no trouble with them; I have never fallen yet (knocks on wood). I am a light guy though at around 150 lbs. They do require some practice and they can place uncomfortable pressure on the ankles but they offer me the most versatility. I can climb any tree anywhere with them; strap myself to the tree and set up my strap-on stand all in about 10 minutes. My stand weighs 10 lbs (compared to much heavier climbing stands) and is smaller and less noisy to carry through the woods than most climbers.

With a climber, you are restricted to trees with no lower limbs and they can slip and cause falls just like any other climbing device. There is a recent thread about some poor guy who broke his back when his climbing stick rolled on him. Bottom line, if you stop paying attention, you can fall and get hurt no matter what you are using to climb the tree.