You are getting a cheaper wire drive system and this is the heart of the system, if the wire does not feed properly it will not weld porperly. The Miller machine has more iron in in which will give it a better arc. This means that on the lower end it will be eayser to get a nice looking weld and on the high end it will have more power for thicker material. Also the Miller machine will give you full output on a 25 amp breaker most of the others will need 30 amps. Miller has a 3 year parts and labor warrenty.

You wont go wrong if you spend the extra money for the Miller, I have tried alot of the other machines you mentioned and none can touch the Miller as far as performance, dependability, and durability. the Miller comes out on top, and as mike said in another response, miller has a great warranty, which you probably wont use.

you need to take a look @ the hobart line.their made in the miller plant side by side and the cost is about 150.00 less than a miller.check www.cyberweld.com i think the 135 goes for 379.00 and the 175 handler goes for 499.00

I have looked at a lot of small shop type of mig welders and for my money two come to mind the Lincoln SP125 which can be plugged into a 110V outlet or the Lincolin 175, requires 230V. Both are exceptional small machines that are made to last. Don't let the small SP 125 scare you off it can handle .250 thick material very nicely, just go slow.