I have upgraded my stick welder once. My first one was cheap and cherious AC only trasnformer. If you can weld with that you can weld with any MMA! It cut out all the time, had glue sticks like there is no tomorrow and generally was more pain than joy to work with.
My next one is Kemppi inververter, old/used/heavy, completely diferent than cerial boxes you buy on supermarkets. Long cables and doees not overheat not cuts out if the fuse is 20A, 16A single phase fuse blows if you weld hard and long, but the inverter hasn't cut out in Finnish weather. Very happy with weld quality and welding feels really easy now. Much more choice with stick too.
I tried a friends Telwin cereal box (size, weight and price) and it does welds fine. Alhough it does not weld biggest sticks that long, that would not really be my issue. The thing with that welder is that cables are very short, stiff, thin. You better keep the inverter in a crate, because othervice you will pull it with the cables and it will fall off the table. So 20% of the weight, 15% of the price and 70% of the usability.
I will not give up on stick welder, It's pretty much the only choice for weldable thick steel profiles on hobby market.
MIG and TIG are not interchangeable and what is really putting me off is the gas, it cost pretty much and if you need Mig and Tig, you really don't cope with one type of gas. But both works well thinner materials. If I would work with old cars, my first choice would be MIG.
My broher bough chinese TIG/MMA/Plasma unit. He tried plasma, never used the stick and is using only TIG, probably spent more on gas and consumables that on the base machine. He say's it is ok.
Pekka
Pekka