George if i was on a site or underneath a car then i would use exactly what you have suggested. it is not wrong for slicing off a bolt, cutting some tubing or removing a door hinge etcetera. In a workshop environment for cutting plate materials i would rather use the proper tool. trust me i have used the tools you say here and have the scares to prove it. Safety is too under estimated and my old workshop tutor would be turning in his grave. These things get you out of a hole when there is nothing else available for sure and as always at your own risk.