I have both Mig, oil filled transformer and an Inverter.
The inverter is a Kemppi, and I have used it on steelwork in cattle sheds on the end of 200m of extention lead with 3.25 rods and it has never tripped out.
You select the machine for the job - conventional stick for 4mm + rods, mig for speed if its not windy or you are in the workshop, and the inverter for portable jobs as it is very light to carry around. Buy one from a reputable welder maker, not a chinese off the net, and make sure the duty cycle is high. Mine has done quite a lot of work and so far has been trouble free. the other thing to check is to ask whether its generator friendly, some don't work well off a generator, but the Kemppi does