If you need a portable...
In 2004 I bought a new 305G Lincoln. 100% duty cycle in 10KW with peak at 11KW. AC/DC/DC reverse, outlets for 110/220 AC. (Built a pigtail to run to my house breaker box during power outages - 70 amps of 220 will get you through the night.) Under load, will work almost 15 hrs on 10 gallons of gas. Runs my LN25 suitcase wirefeed great as well as my plasma torch, also bought the 100' remote for amperage adjustment. Best engine-driven machine I've ever used with a TIG torch - very stable supply. Weighs about 700 lbs and cost $3100 back then.
Have about 2K hours on it and it's aircooled Onan 2 cylinder; oil changes every 160 hrs. Only regret: should've ponied up for the 305D (diesel) instead.
I ran Lincoln SA200s (now called the Pipeliner) for years, but so far, this machine does so much more I doubt I'll ever go back.
Shop box is a Lincoln Idealarc 250 - bulletproof.
The advances in welding tech have really made things much easier, reliable and versatile over the years. Just about anything modern from Miller, Lincoln, Hobart etc. won't steer you wrong. Like many other purchases, you will tend to get what you pay for.
If you buy something from Harbor Freight, well....good luck with that.