Well it could be slow and it often lasted for days. If they meant to speed it up they would break the criminals legs or shove a spear into their heart.Yeah I'd take the crucifixion. The purpose of crucifixion was not so much a slow, agonising death so much as a method to display the bodies, alive or not, for a length of time. It was reserved for political criminals such as Jesus and those whom were executed with him.
It was typically reserved for major crimes. But eventually, as Christians became targets, many were crucified.