Although 5356 filler/electrode is indeed stiffer than 4043, not all 'small' MIG machines have the correct volts-amps relationship to run that electrode. As I said above.
If you are running a 250-class machine, they can usually run almost any wire you want, within size/diameter/amperage limits. The 175-180 class machines, not so much as they can usually only run 4043 wire (RTFM on the specific machine to check). The newer 210-215 class machines, RTFM on the specific machine to see if it supports running both 4043 and 5356 wires.
A 450 or 500 amp class machine can usually run anything you want with the right drive rollers and contact tips and liner.
And as I said above, sometimes you want/need 4043 filler, sometimes you want/need 5356, and sometimes you want/need a different filler. All depends on the base alloy(s) you are welding together, the mechanical want/needs of the welded joint, the want/needs of the color of the welded item after possible anodizing, etc.
Yes on some of the 'small' machines sometimes do offer an 'aluminum kit' with a plastic gun liner (do NOT-NOT-NOT use the standard spiral steel gun liner with aluminum wire! ), u-groove drive rollers, and plastic feed guides. And you still need the appropriate size contact tips, which are ever so slightly larger in the wire hole diameter than a comparable contact tip for a steel wire (o.035 is NOT always 0.035
) But even then, trying to push 10-12 ft of .0035 4043 through a 'small' machine torch can be an exercise in birds nests and frustration if you are not careful and/or lucky (keep the torch cable as STRAIGHT as possible for the entire length sometimes helps).
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