HDMI or Optical for the long run to the projector?

run a long hdmi.  when you inevitably upgrade the apple tv your next device wont have an optical output and youll need the long hdmi anyway.  the 4k hdmi you have is rated for 18gbps and is fine.  

@mcmanus - I don't know if you went in a direction, but I have been getting really excellent results with the Ruipro fiber-optic HDMI cable for long runs.  And it's cheaper than the Lifatec spdif optical.  You can get a 6 meter (19.6 feet) Ruipro Fiber HDMI at amazon for $119.

I actually disagree with Eric on this one.  With optical, the distance does not really matter because there is pretty much zero resistance when using light.  Just make sure you get a really good glass fiber cable, such as Lifatec. Their cost for a 16 foot optical cable is $199, but I'm sure they can make one that is 20 feet. 

With HDMI, distance matters, especially for 4K.  The Chroma 7 is not really the best cable anyways.  The Chroma 7 is only DPL certified for 18G 4K up to 5 meters.  Some of the better cables can do 7 meters, but longer would require an embedded HDMI equalization/booster chip.  

For a short 1M or 2M HDMI cable, I would recommend the Starlight 6 or an UltraViolet 7 (if you want cheaper).  Using a short 1M or 2M HDMI cable would yield much better image quality than a very long cable

Yes, that is exactly what I am asking. Thanks so much. Any thoughts on how sensitive HDMI cables are? I'm using a 7 meter Wireworld Chroma 7 that was $120. Worth upgrading? 

I'm not sure I"m reading this correctly, but if the choice is "Which cable should be short and which should be long?" I'd say go with a short optical, long HDMI.

https://www.bluejeanscable.com/articles/how-long-can-hdmi-run.htm