Interesting topic - I've been shopping for a 10k gas machine myself. The idea of being able to run the sump pump, furnace, fridge and storage freezer whenever the power quits is one motivation. Also, we have a detached garage/shop that has minimal elctrical service, but it's where I want to do the welding, so not having to upgrade service is a big plus.
Being able to take the welder to the work is another reason I've been considering a welder/genny. It would also free up the tractor, not being run off the PTO. It seems that a good 10k generator, either PTO driven or self powered, plus a separate 225 - 250 amp AC/DC stick welder cost more than the combined rig.
I'm starting to line up a lot of "gee, if I only had a decent stick welder" type of projects, so it's getting to the point where I need to make a decision, soon. Sounds like George has had good luck with his Miller Bobcat 250NT AC/DC welder/generator, which is one of the models I'm considering. Another is the Lincoln Ranger 10000. Also, there's the Hobart Champion 10000 DC machine, but I'd like to get an AC/DC machine in case I ever want to expand my welding options to include TIG.
-Jim