i am not an expert by any means, however, i am in a similar position. i can share some thoughts with you. after much thought and reading, a large consideration is cost. an ac/dc unit with enough output and duty cylcle to take care of aluminum (up to 3/8", my guess) will run ball park 3.5K, torch/tank/cables/ect..included. i was interested in an inverter unit, but i think the only advantage is portability, certainly not cost; they are expensive. my concern was wanting or eventually needing to weld "medium" heavy aluminum and spending 2.5K on a unit that couldnt put out enough current. i have taken the postition of using my maximum cost estimate and finding the unit that will best approximate that figure. i am taking a more serious look at lincoln's precision275 with the "ready pak package" (cart and everything but the tank) from an on line distributor, free shipping, for around 3.5K. in that price range, i dont think there are any significant performance differences between the different makers. just my $0.02.
The Miller Dynasty is the only inverter ac/dc that produces full ac amperage at or with full frequency that I know of. In other words, if you want to weld at 200 amps ac you can do so with 250 hertz. This allows a very focused arc with no wandering, especially fillet welds on inside corners. With the sharpened ceriated tungsten no balling is required or necessary. That is if the balance control is 70 to 85% negative. All this power with only 20 amp draw on 240 volt input. You must comparison weld try before you buy these little guys.