Also much lower power and heat.

This is the most compelling reason (unless you really need the range of fiber) - 10GbE can be really power hungry. Each 10G switch port that is in use adds something like 1-5 watts to the power budget. 1 watt is reasonable but most switch hardware isn't nearly that efficient. That could mean 10 watts for every single link if you're using 5 watts at each end. Multiply that by several links and it starts to add up really quickly.