Why buy just a generator when you can buy a generator that also welds? Your best value for power is a combination welder/generator. They're competitively priced compared to stand-alone generators and feature quality gas or diesel engines from Honda, Onan,Kohler and Kubota.
Like a "regular" generator, a welding generator provides 120 VAC and 220 VAC auxiliary power. Typical output capabilities of these products also match up, as a welding generator suitable for home use produces a comparable 3,500 to 12,000 watts. The comparison stops there, though, as a welding generator lets the owner weld mild and stainless steel (and sometimes aluminum) in sections up to 1/2 in. thick or more. Surprisingly, both products cost about the same.