I'm not sure of the meaning
I have my steel type welding machine, so I am planning to have an aluminum type.
The same power supply that welds steel MIG will often weld aluminum MIG. The same wire feeder will not always feed aluminum wire just because it feeds steel wire, but I'm not sure what you're asking or stating?
We've heard from lots of different types of users here, and unless they/we group those posts into types of work; alloys of metals; boats or non-marine work and so forth, we'd have a real difficult time summarizing welding power supplies or their wire feeders for MIG.
Unfortunately, as a resource for decision making this thread is a little bit random. We could look at the discussion to date as one that roams the entire Glen-L design catalog of boats. Some are tiny punts for ponds others may be cold molded offshore sailing live-aboards, and still others may be welded aluminum outboard powered skiffs.
Could we, any of us, say This is the "BEST Design" in the Glen-L catalog? Almost everyone is going to ask "best for what"? So trying to discuss welding power supplies without prefacing the discussion with use or application makes whatever follows into a random walk in the pasture instead of a guide.
Are you summarizing the discussion in the line
Anyway, you just need to check the model the voltage capacity.
I'm not clear there either: but I do agree; there are a list of items to check when selecting a welding power supply investment!
If I were recommending a decision tree or path to making a solid buying selection I'd start with the main use. How long per day will this power supply weld? If longer than 4 hours of solid running per day- then my experience is that there is no reason to buy the home hobby rated machines as they usually have lower 'duty cycle' or power factor ratings. If you're welding 4 hours daily - likely there's business involved and not welding holds up more than one person so pay for the 'pro equipment'. [Lincoln, Miller, Name Brands]
Next I'd want to decide the aluminum welding needs. If there are long seams - hulls, tanks, boxes, walk-ways then MIG is the most commonly used. If the work is all brackets, corners, pipes, padeyes and small tanks then TIG is the main method used.
If you're doing boat work longer than 18' and will climb in and out of the hull during construction then a push pull gun will buy itself about the second day of climbing around looking for tiny 1lb rolls of wire for a pistol type wire feeder. On the other hand if you're working on trailers, bench built tanks and boxes, or small skiffs once in awhile then a pistol or "one pound" gun is more than adequate.
The maximum sustained welding power of the power supply would be next: if you're welding aluminum 3/16" or thicker all day- get a 300A (350A) 60-80% duty cycle power supply with water cooled push-pull wire feed gun. Bite the economic bullet and get the equipment designed to do the work you have planned. If you're not at these minimum thresholds ? There are many systems that may do all you need without the high costs of those in the group above.
In almost all instances there are two generations of power supplies- old and new- 60cycle transformer and high frequency inverter- large and small versions of each welding power supply. Its been mentioned above you can buy a 4-8 thousand dollar power supply that will last your lifetime for pennies on the dollar on eBay. But if you need new then expect to pay for the full value of the new -bells and whistles laden mini suitcase wonder machine.
I have owned dozens of welding power supplies and still have half a dozen spread between the two generations - one huge copper transformer based TIG machine sits next to a suitcase inverter that has more controls than I can use. They both cost about 5k US$ new. One is 30 years older than the other- they both work and I could buy the older one now for 1/10th the amount it cost new and it would weld just fine.
My point here is that costs are related to the generation of the power supply not exclusively that power supply's welding capability. So there are real 'deals' out there if you know what to look for and can get decent testing BEFORE you buy.