Suggest you look at your local used market via craigslist.
I like the Miller Thunderbolt AC/DC machines from far enough back so the leads are detachable. Makes for far cleaner storage. I have one, my second one, love it. Not a large duty cycle, if you need to run a whole lot of stick you might want to get 2 and switch back/forth.
Miller Thunderbolt has a mild edge because it has shunt rather than taps. As Grant mentioned, detachable cables are very nice, I've retrofitted my welders with them. No big deal, standard jacks and plugs are $8 each at my local supplier. Check the cable lengths that come with the machines. Lincoln, in particular, has very short stock leads.
tends to have some good deals. I bought a decent Craftsman 225 amp unit for $50 (a buddy needed one so off it went), Lincoln's go for $75 to $100 and up. The cheap units go VERY fast so you have to watch the lists closely. The Craftsman seller had 3 calls in 45 minutes, I picked it up within an hour of the posting time.
If you are buying new, the DC option is not that much more money so I'd certainly consider going for it. Used machines will rarely have DC, no one wants to spend the extra money for it.
IMHO, DC > Now that I have adequate power to my new shop, I'm thinking of adding an
As for the ubiquitous Lincoln 225A "tombstone") Some people swear by this machine and some at it. I'm one of the latter. I've used these lincolns where the multiple contact switch did not make a good connection and had to be clicked back and forth several times to get maximum output for that range. My preference is the 225A Miller. The output is regulated by moving the core in or out of the transformer.Not only does this give stepless output control but provides a higher open circuit voltage for easier weld starting.