I originally purchased an Atari ST in 1987 as I couldn't afford an Amiga at the time. The ST was about £100 less than an A500 at the time which was quite a lot in those days, especially when still at school and trying to save up for one.
The ST was quite a cool system and most of the games at the time were released for both the ST and Amiga, but the Amiga versions were always better. And the ST had a dire OS called GEM that was probably one of the worst graphical OS's ever released, except for early Windows releases! ST GEM makes Workbench 1.3 look amazing! Amazingly the GEM OS was even released on the PC at the time. I used it once on an old Amstrad PC and it was just as bad.
When I did eventually get an Amiga I practically stopped using the ST as it just wasn't as good at anything compared to the Amiga. I got the good games I had for the ST again for the Amiga so didn't really need the system any longer, but I did keep it for quite some time as there were a lot of demos, utilities, coverdisks and other stuff I had for it that were still fun to sometimes load.
But then the ST emulator Winston came out and I got hold of the complete scene releases of all ST software so the real system wasn't needed at all. That was when I finally decided to sell the system, along with the games, books and magazines I had for it. It had also developed a PSU fault which was common on STFMs. Sometimes it would just power off on it's own and you had to tap the case above and to the right of the keyboard to get it to come back on. Bit dodgy. :hmmm:
And comparing the ST and Amiga size by side in games it was easily clear the Amiga was superior in most respects: Amiga had 4 Channel stereo sound instead of 3 channel mono, 32 colours in game instead of 16, full overscan screenmodes available so that games could use the complete screen whereas ST always had a big border around the edge of the screen similar to 8-bit games (except some games that used special coding to trick the ST into a sort of overscan mode), and the Amiga had much better Copper and Blitter abilities that the ST.
ST fans would still argue it was better, even with all those things mentioned going against the ST.
Don't get me wrong, the ST was a great 16-bit system and far better than the 8-bit systems before it, but compared to the Amiga it was always inferior. I still got many years of enjoyment out of the ST though.

