Atari discovered a fault in its graphics chip once in production. Originally the ST was able to display 4,096 colours, the same as the Amiga. However, the work-a-round for the fault meant the ST could only display 512, and had to have a border that occupied 30% of screen real estate, whereas the Amiga could go full screen. Oh, and the Amiga could genlock as well, so it was used to display titles whilst display the background video (something that you needed equipment costing 100 times more at the time)
The Atari ST had the exact same soundchip in it as the Amstrad CPC, 3 channel, one left, one right, one dual.
The Amiga had its own dedicated soundchip (Paula), that could play 8-bit samples. And was an amazing chip at the time, if anyone remembers noise-tracker, sound-tracker, you may be aware that it was possible to do early dance/house music on an Amiga. The sound on the Amiga was light years away from anything before it, and it was a good 4-5 years after the amiga that the PC got anything resembling the quality of this soundchip.
Whilst the Amiga was indeed not multi-core, it did have co-processors. These co-processors freed up the CPU (just as the graphics cards/sound cards in the modern PC do today), handling audio, video, animation and encoding. So even though the Amiga CPU (Motorola 6800) was indeed slower than the Atari ST, it totally annihilated it when it came to gaming.
The Amiga had multi-tasking. Whereas the ST did not.
The CPU (68000) The Sound (Paula) and The Graphics Chip (Denise) all had to go through Agnus, which provided DMA to all the other chips. (See the modern PC design here, light years ahead of its time). Agnus had the ability to give the Amiga hardware sprites (Via the Blitter, a sub component of Agnus), that also freed up the CPU.
Given the above, it is as clear as day that the Amiga totally thrashed the ST. I know, I had both. And I loved my Amiga....
