by the time i came around (early 90's) the question came down to upgradeability. the atari had midi and seemed to be a neat machine but a 2000 and later 3000 and 4000 could easily upgrade video, processor, and audio. ataris didnt have anything like that.
it is possible to put an 060 accelerator with what 128megs ram, multigig hd, high res true color video card, sound card, and many other goodies into a 2000 with os3.9 ataris always seemed much sleaker but more limited to me. and the later versions (falcon etc) that corrected some of those problems were far too rare.
nowadays it comes down to availability. you can get amigas in many places for reasonable prices. were can you get ataris?
