Composite output even under the best of circumstances will simply be terrible and unbearable for 640 resolution, and just OK for gaming at 320 resolution. The colours generally bleed too, and the overall picture consistency isn't great.
On the other hand, it will be a 1:1 relay (i.e. no frequency conversion at all) so games with smooth scrolling and animation are guaranteed to still look that way(*).
GBS-8220 will do a better job with signal quality but AFAIK it always resamples for 60 Hz output using its own reference frequency.
So, forget smooth scrolling/animation for 50 Hz ("PAL") games, graphics will look unbearably torn apart save for the slowest motion speeds.
But even for 60 Hz ("NTSC") games, the result will not be 100% perfect, because of a tiny but inevitable mismatch between the Amiga's 60 Hz and the GBS's 60 Hz output. This will cause a frame "hiccup" every once in a while, although for the most part scrolling/animation will look smooth.
So, if the Indy ECS is not an option, you might want to use both(**) methods:
- A520 for simple gaming via composite, where picture quality may not matter that much, and have the advantage of perfect motion regardless of 50/60 hz, which is a must for enjoyable gaming
- GBS for Workbench/Apps usage, where motion smoothness doesn't matter a lot but picture clarity (esp. at 640 resolution) does.
(*) LCD screens exhibit motion blur on their own, even when using correct frequency, this has nothing to do with the signal. Maybe with newest models this isn't noticeable anymore, but every single model I've seen so far (no matter computer monitor or large TV) suffers from this too much for my liking. So, I heartily advise that a CRT display be used.
(**) Using a suitable "Y" cable, a DB23 port "doubler" or maybe even taking advantage of the internal video slot as a secondary RGB source. A more hardcore option would be to mod the existing composite output of the Amiga 2000 to support colour output.
