Howdy...
The key to purchasing an electric welder of any kind is to ensure the unit you purchase, has a high duty cycle for the material you want to weld together.
If the vast majority of the work you do is 1/4" plate or thinner, a welder that has a 60% duty cycle at 3/8" might be okay for you, as at 1/4" the duty cycle might be 90%. When you start welding, you're going to be starting and stopping constantly anyway, learning the technique applicable to that unit as well as the settings and what they actually do. So a duty cycle is okay.
Once you become proficient in electric welding, and you're projects get larger (as they always do /forums/images/graemlins/laugh.gif) you will want a higher duty cycle, because you have the confidence and the ability, to weld long beads as dictated by projects.
While most materials are joined together in small beads, as often times there is no need to weld a 6' long bead... but there are cases that do require such - enclosures that have to contain liquids for example. Homemade snow plows, and thick-material body work like bumpers and such. Those you could seam the pieces together in one shot because they are thick enough not to warp. Stitch the smaller stuff.
As far as what kind of welder to buy... there is no doubt in my mind that Tig welding produces the prettiest weld. A practiced Tig welder can make beautiful swirlies all day. Also, Tig is excellent for non-ferrous materials like Aluminum and Brass, because the heat is so localized, the material you're welding will not warp as easily as some of the other electrical welding methods.
Arc welding in my opinion is good for heavy duty, large sized stuff. If I had to weld a tooth onto a bucket loader, Arc welding would be my first choice. The penetration and weld puddles can be very large, making for a nice weld the first time around. Arc welding also is environment resistant - meaning you can get nice welds in the rain, scorching sun, even if the part has some rust on it. It's so hot that stuff burns off. This is why I think tradesmen often prefer and learn Arc welding - it's a great process for people in the field. And it's simple too... a big transformer and a welding rod.
For the hobbiest however, I'd lean towards wire-fed mig welding, with gasless and gas capability. I find flux-core welding wire good enough for more applications, even with the smoke and splatter. I have a small battery operated fan I put near my work, drawing the smoke away allowing me to see the weld puddle better. For stronger, and cleaner looking welds, using gas (CO + Argon typically) helps you achieve this. Mig is less forgiving about cleanliness as Arc welding, but the heat is more localized so your weld puddle is smaller and more precise. Nothing like Tig, just comparing it to Arc.
And wire fed mig welders with the gas capability are cool because you can buy the unit now, knowing that someday you might want to use bottle gas and all you have to do is buy the gas kit and attach it to the back of the unit. So you can purchase a larger, better unit up front without the gas attachments, then as you need it down the road, spring for that.
While I can't do it, a friend of mine who I'd consider an artist as far as welding talent goes (he owns a large auto body shop and started working there as a kid when his father owned it) can actually weld aluminum with my wire-fed mig welder. The gas is different, the welding wire obviously is different, but his welding ability made aluminum mig welding look *almost* like tig welding. Almost /forums/images/graemlins/laugh.gif
But regardless what welding unit and method you choose, practice practice practice. That's the key to good welding. Find things to weld!
