Some observations and a question.
O/A will cut non-stainless steel only. You will need something else to cut stainless steel, aluminum, copper, brass, etc.
When cutting angles and tubes (regardless of metal type), I find a chop saw far more convenient and easier to use than O/A. For cutting aluminum, a woodworking table saw with a carbide tipped blade is hard to beat.
O/A can soften metals so they can then be more easily bent with some other means, maybe by hand. For heating metal to the softening point a propane torch can often do the job for me. In many cases metals can be bent without heating if you have an inexpensive bending machine, and by not heating you avoid scale formation and annealing (softening that persists after the metal has cooled to room temperature).
Turning on a propane torch is simply a matter of pressing a trigger, while turning on the O/A torch involves the following steps:
1- Select and install torch tip according to amount of heat desired. 2- Open valves on two gas tanks. 3- Adjust pressure on two gas tanks according to tip size selected. 4- Open the acetylene valve on the torch and light the flame.with a separate flint. 5- Open the oxygen valve on the torch and adjust flame to desired intensity and appearance. Why go through all that hassle with O/A if the propane torch is up to the task? That is the question I ask myself every time I need to heat something.Good old brazing. Brazing is weaker than welding in many cases. Brazing requires more preparation (cleaning, fluxing, aligning, clamping) than welding in many cases. Brazing temperatures are high enough to anneal most metals. Brazing produces more heat distortion that welding in many cases. You will not be brazing steel to steel if you can weld it. You will not be brazing copper tubing if you can solder it with a propane torch. Brazing is good if you can't weld, or if you need to join dissimilar metals and soldering isn't strong enough and annealing is tolerable.
Now the question. Isn't MIG with fluxcore wire supposed to do well outdoors on dirty rusty metal?