Also the ST gets dinged for being less powerful, but it was actually significantly faster than the Mac at the time and with an add-on could even run Mac applications.
I never even had a colour monitor for my ST. The paperwhite monochrome screen was to die for back then, and sure beat the interlace hi-rez experience on the Amiga.
And the ST was a few hundred bucks cheaper. Price per mhz, it was a great machine.
My take is that both the Amiga and the Atari had a plethora of expansions and, without having any numbers to show, I think the Amiga won out in the expansion race, from 040 cards for the A500 (AFAIK no 040 was available for any Atari until much later) to the Video Toaster.
Both machines were hard to evolve because both their designs encouraged software that was tightly tied to the hardware. VIDEL and AGA were both desperate and, ultimately, fruitless attempts at having the cake and eating it: sticking to custom chips was needed to keep backwards compatibility, but they made the machines both too expensive and too underpowered to be competitive.
Amiga went the road of being console turned computer, and the expansions only created havok with support. Even A500 Plus had issues.
Sadly - it also affects community - the IP rights for Amiga are mess, the recent issue with Terrible Fire extensions - for some reason a lot of bad blood in a very bold and interesting system made by Atari engineers.
And, of course, there was what seems like a cocaine-fueled endless sequence of management blunders that drove the company into the ground.
ECS could address more chipmem but wasn't slower than OCS. You couldn't add fastmem in the trapdoor port, but that didn't matter much since those expansions weren't good enough to impact the speed (trapdoor fastmem was usually called slowfast). The problem was rather one of incompatiblity: some programs written in the 512+512 kbyte era simply assumed they could allocate fastmem, which typically wasn't available on the 500+ and 600.
> After ECS came AGA, which pushed the boundary further again (but, at this point, memory constraints were not so terrible).
AGA, like ECS, could address 2 megs of chipmem. However, it had higher bandwidth and was much faster than ECS.
My point is that even though the ST/e was, as you say, a simpler design in many aspects, Atari still had to equip the Falcon with a YM chip and put support for planar 15 kHz video in VIDEL to maintain backwards compatibility. They faced the same problem as Commodore: their machines were mainly home computers used for games and other software that banged the metal and people expected this to work when upgrading. They also shared a lot of the same problems when upgrading the architecture even slightly, such as with the A3000 and TT030: programs that didn't work with newer versions of TOS/DOS and programs that didn't work with 020/030.
Both platforms are expandable with things like RTG graphics cards, sound cards, CPU cards etc. (in fact I'd argue the Amiga architecture with Zorro, video slots and CPU daughterboards was designed to be vastly more expandable than the Atari) but for most users that didn't matter: if the games they wanted to play didn't work, what point was a 24-bit display that cost more than the computer itself?
Besides, even without keeping backwards compatibility, rolling your own silicon was no longer a viable option financially. Tramiel's vertical integration was a good idea in the 1980:s but the hardware market had shifted. Commodore could've made a triple-A machine but it still wouldn't have been competitive, neither in price nor in performance. The niche markets utilizing the unique features of Atari (MIDI) and Amiga (DTV) weren't large enough and a new architecture that would deprecate all or most existing software (and many peripherals) used by hobbyists would probably only serve to push the home user base towards the PC anyway.
Additionally, having the copper, sprites, scrolling, HAM and planar graphics modes meant that backwards compatibility is harder - just look at the difficulty of emulation for both of them.
The Amiga graphics layout is also (slightly) more difficult to work with, there's a trick for the ST to do quick chunky-to-planar (C2P) conversion, check out the texture mapping in Thunderdome demo (http://www.pouet.net/prod.php?which=64503)
All said, yes the Amiga had more expansion cards for it, but the central bus system was a bottleneck as for the majority of Amigas, you had to use the built-in graphics, if you look at the a1200, the AGA chipset was a poor upgrade over the original chipset, hampered by backwards compatibility and the expense to needing to add a separate (fastram) bank to bypass the system bus for speed.
As far as retargetable graphics goes (ie. VGA-style cards), the ST was ahead as GEM allowed this from the start. That combined with the much simpler design allows a newer machine to be much more powerful as it has to worry about backwards compatibility less.
The Atari Falcon bears this out, a stock Falcon can manage to run Quake2 at 10FPS odd, a stock a1200 even with fastram can't get close. The Falcon was actually developed using an ST with a processor socket, bearing out the simpler architecture could be abused more :)
TBH the Falcon could have been much more, but Atari were broke and cheaped out on the 16bit bus, could've had 24bit VIDEL at 800x600 and run Quake2 at 15-20FPS for £500 in 1992. Add a cdrom with multiTos (effectively unix with a GEM frontend) and you'd have a competitive machine even against the PC of the time.
These things meant that later the Atari community and Atari themselves were able to extend the OS in a proper multitasking almost Unix-like direction (MiNT and MultiGEM) and bring it to new hardware, and new display formats and architectures, etc. Provided the applications being run were cleanly written (well, that's a big caveat...). For example -- we can now run TOS/GEM on an Amiga, that's pretty neat (though totally pointless).
In true Tramiel fashion they shipped the cheapest simplest thing they could. But it was something they were able to iterate on -- unfortunately they just did this too slowly. As others have pointed out, the Amiga had amazing hardware from the go, but its architecture became somewhat tied to that original hardware. It was more like a video games console than a workstation. They had a few years headstart on everyone else and then having (then dated) specialized hardware became a liability, not an advantage.
I built MicroGNUEmacs as a desk accessory so that I could run it at the same time as other programs.
I never saw uemacs compiled as a DA. That would have been a nice trick. The only microemacs I used on my ST was not a windowed application, was console only.
I chose the MicroGNU variant as it did parenthesis matching better than the alternatives. I ran it alongside Franz Lisp that I had also made into a GEM application.