So this is a 2-pronged "best-of-both-worlds" approach where you have the external gas shield, and also the slag cover protection all-in-1
(I think)?
When I last did stick welding, I always had to "imagine" where the puddle was under the slag. I considered the weld very good if the slag peeled up as a slightly curled strip all by itself. I was thinking the "in gas" welds let you see the weld, sans any slagould cover, and that be a "good thing".
If by "this" you mean FCAW-G, then I would say that it is a great option, but it doesn't come without it's own set of drawbacks/compromises. Disadvantages include many wires susceptible to moisture-entrapment that seeks out to penetrate the flux in the middle of the wire, leading to issues like porosity or "worm-tracks". They must be kept away from moisture in the air - even regular humidity in the air will do-them-in in a few weeks if not careful. There is also the removal of the slag itself; not particularly difficult as it comes off similar to E7018 where it can lift-off by itself, or otherwise is easily chipped off, but none the less it is there, where as with normal solid-wire MIG and C25 gas there is no such clean-up to attend to. Also, FCAW-G wire is meant to be ran at high amperages, since it's benefits of high-deposition and deep penetration require a high-energy electric arc (referred to as spray-transfer, or spray-like transfer). So even for a thin wire like 0.035", you need to be up into the 190-230A range to take advantage of it's capabilities and to avoid the production of large amounts of spatter. It doesn't run all that well below 130A or so - you end up with a lot of large spatter BB's to clean up afterwards. Essentially useless for thin metals 1/8" thick and thinner. As for seeing the weld puddle with solid-wire MIG without having to deal with slag, yes that is an inherent advantage of it. But at the same time, slag does not necessarily have to imply "limited visibility" of the weld puddle. When everything
as a whole is not set up properly, from the welder to the the
weldor, then it can potentially become an issue. But set-up correctly, a slag-bearing weld procedure can be just as easy as one without. It surely depends on experience and prior knowledge, trial-and-error, knowing proper welding operating parameters and not just half-a*@'ing things, etc, etc.
On stick welding, if you had to imagine where the puddle was under the slag, that's because either you weren't using enough amperage to have the arc pressure (as in literally, the electric arc produces a pressure against the weld pool) work for you and push the slag back past the weld puddle, or there were other issues in technique such as incorrect electrode angle, travel speed, and/or arc length. Different electrodes have different-behaving slag systems and require different operating parameters to properly run and manage the molten weld puddle. E6013 for example, has a very thick, runny, fluid slag that will creep up on your weld puddle if you're not careful with the above aforementioned attributes. Then that is when the distinction between the molten weld puddle and the slag begins to deteriorate and potentially ruins the weld bead if you get slap entrapment.
