I usually render my movies for in-str displays as H.264. But this color combo seems to be the problem.
I´ve just made some very simple animations, two different grey solids in background and then som orange texts on top made as .ai-files. (Same result eith .psd and .pdf)
The only render that looks really good is the one rendered through Render queue as animated.
That one is sharp as a knife, the rest looks like Danish LEGO.
Does anyone know the reason for this or have any ideas how to output this with better quality?
Please upload a PNG instead of a JPEG -- the JPEG is adding additional compression artifacts that make evaluation difficult.
That said, I suspect the issue you're seeing is caused by H.264's chroma subsampling.
With chroma subsampling, color values are encoded at half-resolution (or worse) while the brightness values are encoded at full-resolution. This takes advantage of the fact that the eye is more sensitive to changes in brightness than it is to changes in color to reduce data size. However, this leads to jaggies for things like red text on saturated non-red backgrounds where the edge detail (brightness) is encoded at a higher resolution than the color, so edges don't align perfectly.
Ae thinks in RGB, which has no chroma subsampling, so your previews will always look clean.
Chroma subsampling is often unavoidable for final delivery, so while you could try other compressors to see if they do a better a job with this material, you may be better off adjusting your design for this reality.