i just prefer the gas because it comes out "prettier"
u dont have to scrape off all the slag like u do when u use teh flux. a good starter mig setup with gas shouldnt cost more than $500.00 (this includes the bottle, gas, cheap helmet, and wire) we have a lil hobart 135 MIG at teh house. it works pretty good for small stuff....up to 3/16" thick stuff. it runs on 110v and is rated up to 135amps IIRC. it came with a flux wire spool too, but ive never used it.