Well to compare steel welding to aluminum welding the way I describe it to people I am teaching is:
Welding steel you have a sweet spot it will fuse that is the size of a barn door, you almost cannot miss, and if you do the next shot at it you won't. Welding aluminum the sweet spot is the size of the door latch you can hit it but you won't on accident it takes practice and you have to know where it is. Once you find it though the difficulty is reduced and it gets much easier.
This goes for tig and for mig (spool gun or push pull) systems although MIG aluminum welding the material being welded doesn't have to be quite as clean, and the sweet spot is a tad bit more forgiving.
All in all a beginner can be taught to weld aluminum but teaching yourself will most often result in frustration
. Thats my tip of the day