I somehow can't tell the difference between Tandy 1000 graphics and Apple II GS. Are they both 8bit or 16bit? Or they different bits?
This "8-bit/16-bit/whatever" thing really needs to die, or at least this misconception that the aesthetics people that associate with said terms has *anything* to do with the CPU in a given computer. The Atari 2600 and the Turbographix-16 both have 8-bit CPUs, even both 6502-family derivatives, but you sure as heck wouldn't think they belonged in the same category based on their graphical output capabilities.
(Nitpicker trivia: the first popular "16 bit" gaming console going by the width of the CPU data path and registers was the Mattel Intellivision. Not the sort of thing that usually gets lumped alongside the Sega Genesis.)
Anyway, that rant aside... the IIgs and the Tandy 1000 are *very* comparable machines. As mentioned above, the IIgs has a much broader color palette (thanks to its use of an analog monitor with 4 bit DAC resolution for each RGB color) and the tricks like being able to swap color palettes per line, but in the end both machines are limited to 32k of video memory and their CPUs are roughly in the same ball park in terms of raw horsepower. (You could kick off a violent religious war by asking what's
actually better, an honest 4.77 or 7.16 mhz 8088 or a 2.8mhz 65816 saddled with a 1mhz bus between it and the graphics hardware, but realistically they're within shouting distance of each other.) Unless a developer really leans into the advantages one of the machines offers over the other you're probably going to be able to run roughly the same games on both with roughly equivalent quality.
The IIgs did have a much more capable sound chip, however. Basically no contest there. Tandy sound is fantastic compared to a plain IBM PC but that's about it.