Hobart and Lincoln are both owned by Illinois Tool Works. The company hosts a very informative forum at
https://www.hobartwelders.com/weldtalk/ that discusses all manufacturers and processes.
In short, the Hobart line is sold through "box stores" like Tractor Supply Co. Miller is only sold through welding supply distributors (like AirGas or Praxair, for instance). Note that Miller distributors do service the Hobart line. You might also note that the same distributors that sell/service Miller also sell/service Lincoln's products.
The (presumed) differentiation id that Hobart's products are geared for the casual user (Farm, Hobby, incedental maintenance) - and you can tell that from the Duty Cycle ratings - they aren't production machines.
Miller units are (typically) production units - again, look at the duty cycle and compare to the Hobart counterpart. In a hobby environment, the first miller you buy will likely serve the next four generations (your great grand kids!). As you noticed, however, Miller's tools are priced accordingly.
Lincoln doesn't differentiate its Hobby machines from its Industrial machines in teh same fashion. You can buy Lincoln machines at Fleet Farm as well as at the welding supply store - but you won't find the higher-duty-cycle machines in the box store, nor the "toy" machines at the distributor.
For welding a tube fram kart chassis (etc.) do not be afraid of the Hobart units. Compare specs as best you can...
My 110 wire feed welder is a Lincoln Weld Pack. Its shortfalls are...
1. the wire feed rate control goes from 1-10 (10 being fastest). i spend 100% of my welding, regardless of how much heat I am pushing, betweensettings 1 and 2. It makes the wire speed control VERY touchy, and therefore a PITA. If I were buying again, I would make sure that the speed control was "better" than what I have.
2. The power settings are "fixed". the settings are labeled A, B, C and D. This is less than optimal, because sometimes wish I had "C-and-a-half". If buying again, I would look for infininely variable heat to solve this problem.
One last thought - one that didn't occur to me until I started looking at TIG machines... Often, the welding supply distributor will have used machines that they have been taken in on trade, etc. It is a very educational experience to visit with these guys. Go to your local distributor, tell them what you are welding, how often you do so and what your budget is. They might have a used unit that will suit you. At a minimum, you will get insight and you will get a feel for their ability to service any unit, new or used, that you buy (from wherever you buy it).
...on the other hand, don't expect much help from the box store folks. They just don't know.[/QUOT
Thats alot to take in but aswers most of my questions. Thanks