With a green field installation 10gbps network (no legacy equipment to support), why would one select one physical medium over the other? If left to impulse, I'd probably go with fiber optics over twisted pair because it is new and exciting. (Sparkly Pony!) But really, this should be a rational, logical decision.
I've very much interested in the "why" behind answers. E.g.: "Fiber performance can be degraded when placed near Kryptonite", "TP is 1000 times cheaper" etc.
(Background: I ask because I have a need to upgrade our Internet web/streaming servers network infrastructure at the data center.)
Best Answer
If you're using copper, your cable runs will be limited. (15m for twin-ax, 55m for STP/UTP). Also, bear in mind that you will need Cat6 if you go with the STP/UTP option. (Cat6a will allow you to run 10G/copper at distances of 100m).
The other thing you should look into is the relative cost of hardware. Most 10G fiber line cards are modular, with the optics being separate. This increases your initial outlay, but reduces replacement costs as generally optics fail at a much higher rate than line cards. I don't know if there are modular copper cards, and what the relative failure rates of transceivers vs. line cards are when using copper.
My bias would be fiber for all infrastructure (i.e. network-network) links. Having recently participated in a new DC build where we used Cat6 for all host connections, (even though we're only running at 1G), I'm not convinced by it. The cables are heavier and more difficult to run (less flex in them). The connectors, despite supposedly being the same spec as RJ45, seem to be slightly larger, which makes insertion/removal difficult.