I have a Miller Dynasty 350 with a water cooled torch which I seldom use. I have an old Miller 251 with a push pull setup that we use for most structural welding we have to do on our trailers. A couple of years ago I bought a Miller 212 with a spool gun dedicated to it. This is the welder I use for everything I do. I don't weld a whole lot at one time and I guess the spool gun would get heavy over an extended period. Occasionally I have to use the 251 tp get into a tight place. But the 212 is my favorite for welding aluminum. Of course you get used to the machine you use the most. One of the local welders here uses nothing but tig on aluminum and won't hear of wire. The factory that builds our aluminum trailers uses nothing but wire for new construction as well as repairs.
