With the mig you will have more control over temp and wire speed. The mig feeds the wire to the end of the gun and if you have shielding gas it sounds the wire at the tip for a better weld.
The arch welder, if I remember correctly, is fed in a stick form by you. They usually have higher welding temps and less adjustably which makes it more suitable for thicker metal. There are attachments that you can buy for arch welders that make them easier to use with thinner metal, but by the time you buy the attachments you could have bought a mig in the first place.
I have had a Hobart, Miller and Lincoln welders in the past all work well, The Miller is better and American made, but as stated before the Hobart is very similar, just different warranty.
Unless you want to run a 220V line I would stay with the 110V powered welders. The main difference in most welders price wise is the duty cycle, which means how long you can continually weld with it, without stopping. Unless you get really good at welding automotive stuff you will probably not have to worry about that since you constantly stop a start for stop welding and staying away from heat damage.
Check your local Tractor Supply or Welding shop, they might beat Northern's price by the time you pay for shipping.