Dual shield is the best set up for mig wedling for sure, it is used in almost any fab shop out there, and is the MIG equivilant for SMAW 7018 in quality and strength.
about innershield- it has its place in the welding world, just depends what you are wanting to fab.
Dual shield is superior than innershield in most applications, and I think GMAW (mig with shielding gas) is better than innershield in most applications.
"Although the Innershield process has been displaced in many
areas by gas-shielded processes, Innershield continues to be an
important process for steel fabrication in many markets.
Innershield is the primary means for structural steel building
erection in the United States. In any shop or shipyard where wind
is a problem, Innershield can be a viable solution. Pipeline
fabrication is often done with Innershield because it is done
outdoors and shielding gas is sometimes difficult to get to these
locations."
(taken from Lincoln Electric's website)
