Kix,  In my experience a 1/8 gap on those thicknesses will challenge a lot of guys no matter which process you choose. 

There is a lot to be said for both, as I am sure you know, both pro and con.  I think my money would be on the pulse though I haven't used it in production, just demo.   GMAW-S will do a very respectable job as long as it is set up right and the operator is experienced.  Having fewer variables than the pulse system, having been around longer as well, I think more guys would start out better with the short circuiting.  On the other hand, with a little training the pulse would catch back up to the training/production curve pretty quickly. 

So, I stand upon my first statement, though not from vast personal experience, that my money would be on the pulse.

Just my two tin pennies worth.

Have a Great Day,  Brent

Hey Kix!

GOOD LUCK!!! :) :) :) "Let er fly boys and girls." WTF???
Minimize or eliminate them and then you might start heading to where you want to be especially with sheet metal production runs!
One eighth of an inch gap and you think there will not be a significant amount of distortion, not to mention residual stresses afterwards???
Yeah RIGHT!!! Like I said before... GOOD LUCK!!!

Unless that is, if you're going to have some sort of set-up with heat sinks of some sort along with the appropriate fixturing yet even so, unless your application does allow for some distortion/warping, you're still gonna have quite a bit of shrinkage in some - if not all of those joints with such large gaps considering the sheet metal gauges you're working with.

Minimize or eliminate the gaps is the best course of action to take which should not be too hard to do especially if the gaps are that size, then you could use the GMAW-P welding power source package that "floats your boat - so to speak!!!" :) :) :) 

Respectfully,
Henry

Hey Ray!

SST (Lincoln Surface Tension Transfer) and RMD (Miller Regulated Metal Deposition) are specifically designed to deal with open roots... Both also have proven trials with stainless open roots without gas backing. (depending on service and code this may be a good option)

GMAWP is going to be faster and more productive than Short Circuit Mig. 

The fusion issues sometimes associated with GMAWP should not be a problem with the thicknesses you describe.

Henry makes a bunch of good points...  Planning on inconsistant fitups is going to make for headaches in production no matter what type of power supply you get..

Stainless is a notoriously poor short circuit material... If the bulk of the work is stainless than GMAWP with considerations of RMD or STT might do.. (RMD, STT, GMAWP all will run less expensive shield gasses than the helium rich mixes commonly used for short circuit and stainless)

I'm sure you can get on-site demos of all the technologies mentioned.

this doesn't answer your question directly.

but I'm curious if GTAW has been considered at all.

only because 12 thru16 ga are readily fused via GTAW, and in the time studies we did it was faster than GMAW for stainless steel.

I have no direct experience with GMAW-P other than hearing words of discouragement with the process on thinner gauge material. Also as noted before 1/8" is a LARGE gap for material, that means the gap would be wider than the landing of the material. Would be very hard to accomplish consistantly without the use of a backing.