What are the disadvantages of a gasless MIG

I was wondering if anyone could make clear the advantages, disadvantages and limitations of gasless (flux core ) mig welders?

You dont need gas, lol, sorry, i use one all the time, gasless you can use outside in the wind where gas is not so good, new steel is best for gasless, thinner steel is better for gassed, there was a big post about this a while back, do a search, very informative

Andy