Mac Mini 2018 Ethernet option 1 vs. 10 GB
10 GB/s transfer speeds are faster than 1 GB/s transfer speeds.

From the Mac mini purchase page 


  Mac mini has some of the most versatile ports and connectivity options
  of any Mac, allowing it to serve and adapt to a wide variety of
  situations and workflows. Mac mini comes standard with
  10/100/1000BASE-T Gigabit (1Gb) Ethernet using an RJ-45 connector. For
  network connections that are up to 10 times faster, Mac mini has a
  10Gb Ethernet option. The 10Gb Ethernet option supports Nbase-T
  industry-standard 1Gb, 2.5Gb, 5Gb, and 10Gb network speeds using an
  RJ-45 connector. With 10Gb Ethernet, Mac mini will provide higher
  connectivity bandwidth for sharing files between desktops, working
  with high-performance network storage, or large-capacity data loads.