A stick welder is probably best for what you want to do. No need for messing with wire and rollers and all that, when you just want to tack a few peices together. Just a lot simpler set up with much less maintenance. Turn it on, stick a rod in the stinger and go to town. When your done, turn it off
So of the ones you've listed I would pick the first one (CH 225 MAX). It has enough capacity to do other work if you ever feel the need, and is very well suited to what you want to do. If you were planning on using it a lot I would recommend you look for a Lincoln AC 225 , which is a little more money, but for what you plan the CH will probably work fine. It sounds like a decent machine.
I wouldn't choose the ARC 140 for the simple fact that it lists useable electrodes from 1/16" to 5/64". Good luck finding them. Most common stores (TSC, lowes, home depot etc.) only carry from 3/32"-3/16", sometimes up to 1/4" but not very common. You have to find a pretty dedicated welding store to have a big enough selection to find those itty bitty ones. It also lacks capacity to do a much welding. It would probably work for what you plan on, but you might as well buy something with a little more ass in case you need to make something for the shop sometime since your spending that much anyway.
The chicago electric welder has less capacity than the campbell hausfeld, and I'm just really hesitant to buy anything that expensive from that line of tools. I've never looked at their welders, and don't know anything about them, but its not a brand thats known for quality. Don't know what kind of warranty it has either. Campbell hausfeld seems to make decent tools from my experience. My dad has a compressor and some air tools by them, and they've been pretty good for the money.
The MIG you listed looks like it would do what you want, but I really think it would be more hassle than its worth for what you plan on doing. The real advantage of a MIG is either getting the gas shield so you can cleanly weld thin stuff, or weld aluminum. Or if your using flux core, the adantage is running longer beads than you can with a stick welder. None of that really applies to what you want to do and the up keep on a MIG is 100% more work than a stick. You've got to keep the contact tips clean, replace them when they burn up. Keep the wire from kinking, or tangling in the feed rollers etc. Its just not worth the trouble for what you're wanting to do. At least in my opinion
