Fiber is ALWAYS better than Ethernet. Look at what Playback Designs is using with Plink. What do they know about DACs and streaming.
Funny thing is you DO NOT need to spend $5k to make a great fibre streamer.
Ethernet is great for dealers since you can make it sound great with a lot of other costly things. With fibre, it is rather boring since a single relatively low-cost item will suffice. I have beem on the fibre bandwagon a very long time.