Propane allows you to do more cutting for less $$, at least going with our local prices here. I've never really noticed it taking longer on a job than acetylene (we use both at work). One minor thing about propane is that the flame goes out a lot easier than it does with acetylene, so if you do most of your cutting outside in a really windy area, that -might- be enough of an annoyance for you to stick with acetylene. We use acetylene for our smaller torch/bottle set that gets rolled around the yard just for that reason.