MIG welds are strong, it has a lot to do with prep and the person welding.I just got a SGC1060, got the 3rd function valve isntalled today and got it home. I need to add 2 short hydraulic lines and Im ready to go.
As far as welds, I havent looked it over good yet. MIG welds are stronger than TIG though. In MIG, the wire gets penetration. In TIG, thats more a surface weld and a filler rod is used to filled gaps or holes.
I've seen many MIG welds that look great but would pull apart easily.also porosity seems to be more likely than other weld methods.
To each his own on welding methods. In our shop, MIG was not allowed on any x ray quality weld. Only ARC and TIG methods were used.
I hope your grapple is as useful as ours is. It saves a lot of labor.
Have a great day.