DAC (copper) is considered lower latency than fiber. Electric/optical conversions arent free. 10Gbase-T however loses out due to the way it encodes frames onto the wire. Overall though your other stuff probably adds so much latency that this will not matter at all.10g copper or 10g Fiber, that alone makes a big difference in latency, Fiber being better.
Yes DAC would be faster I guess but I don't have the figures.DAC (copper) is considered lower latency than fiber. Electric/optical conversions arent free. 10Gbase-T however loses out due to the way it encodes frames onto the wire. Overall though your other stuff probably adds so much latency that this will not matter at all.