What is your experience level welding, what type of projects do you want to do, what level of electrical service do you have access to, and how much do you weld? All questions that affect what is the best machine for you...
AC buzz boxes are cheap, easy to find used, and, if older, may last forever! But, over time, more has been welded with them than any other type of "modern" welding. If your uses are only occasional, that may be enough, and a 220 volt, 250 amp welder will do a lot of welding. Why spend more than you need to?
AC/DC stick welding provides maximum flexibility - lots of specialty rods available and you can weld on "dirty" metal. Don't have to worry about shielding gas, etc. A little harder to learn than say, MIG, but still plenty capable. Again, a 220 welder would do most any project you would practically do.
MIG is the simplest process to use, but your metals have to be CLEAN - MIG lets you make welds that may look good, but may not have much structural depth - easy to use, but still have to work to use properly. If you are doing auto body work, a 110 volt mig is probobly the best bet and portable, but 220volt gives you more flexibility. I wouldn't dop any structural welding with a 110 welder...
I learned a long time ago on a stick welder. I use a 110 mig for auto body and light work, but still do most heavier welding with a BIG, heavy idealarc 300 (stick and tig) work. The idealarc requires a 100 watt breaker, and weighs over 400 pounds, and I got it cheap. Whatever works for you.....