HDMI versus USB-C to DisplayPort

For the 2018 Mac mini, using a USB-C to DisplayPort cable (connected to one of the mini's Thunderbolt 3 ports) would provide the best potential resolution for an external display: 5120 x 2880 @ 60Hz (aka, 5K).

The next "best," would be a USB-C to HDMI: 4096 x 2160 @ 60Hz (aka, 4K)

Displayport seems to work better. However, now HDMI is not far behind.

Now a lot of medium/low end monitors only have HDMI and maybe one displayport input.