Yeah, it really depends on what you are pluging. And of course how big the hole. On large holes a half inch or better using a simple pair of offset tin snips you can do just about anything in seconds using the exact same thickness as the body metal you are working with.
"Offset" tin snips are often over looked by bodymen for some reason. You can cut across the middle of a sheet of metal for three feet cutting a nearly perfect line with almost no distortion. OR, you can cut a round piece the size of a dime shaving off a fraction of an inch with each cut. A pair of sharp offsets will allow you to shave off a strip of metal from an edge a 32nd of an inch or smaller! I honestly don't understand why more guys don't have them in their boxes. Where as straight tin snips I find are almost useless!
One of the MANY tips I got out of a GREAT video by Ron Covell "Basic Techniques of working with metal" is to use the hole punch to make the plugs! A "Roper Whitney" hole punch is a VERY valuable tool around a body shop or garage where you are doing fabing or body repair replacing panels that sort of thing.
The cool thing is the punch pushes the metal thru it's die and leaves this perfect round piece of metal with a dent in the middle where it shoved it thru the die. I threw them away never thinking a thing about it until I saw the first five minutes of this video. In it Ron shows you how take a hole in a body and drill it to the size hole you will punch in a blank sheet of metal with your punch. So, now you have the hole in enlarged to the perfect size. You take the little round piece you punched out of a piece of scrap and you lay it in the enlarged hole on your body. You back it with a dolly and then set this "plug" in the hole. You then tap on the dent in the plug flattening it out. This flattening makes it larger spreading it out to fit tight in the hole! You then weld it around the edge and WHAM, hole filled!
You can even get square punches for this punch! A VERY good tool to have around! I have both the "jr" and the "XX" and have used them reguarly for years. I couldn't imagine working around car and truck bodies without them.
There are cheap versions, buy them if you must, but I sprung for the real thing and have never said "I wish I would have bought the cheaper tool".