Not necessarily. The DC inverter machines can be bought up to 600 amps if you want and have the money. But like the Everlast PowerARC 200...It sells for $350.00 , weighs less than 30 lbs, scratch start tig capable and is a commercial class machine. 200 amps is way more than enough to handle 95% of the welding jobs most commercial customers have even in the oil fields.
BUT transformer machines that have AC/DC do have much less amp capability in DC just because of the way they are manufactured with the rectifying system that is administered to the AC current.
DC current is much more stable and yes, because of the DC polarity, the electrode gets the majority of the heat concentrated on it so melting is smooth and regular. On AC, the heat is shared 50/50 60 times a second. During the time the arc cycles or "reverses" the arc literally goes out and then reestablishes. There are very few real reasons anyone will ever need an AC current when stick welding. It makes a much lower quality weld with more slag and inclusions in the weld. One time that AC is usually touted to be superior is controlling arc blow. But proper cable and clamp arrangement and a little skill can prevent this rare occurance in DC as well.
