Wondering if any of the networking gurus on here could help me with something.

I have a NAS (Synology) I use for backing up Roon, among other things. Trouble is, every time I turn the power to the networking components off the IP address gets changed, so that I have to go back into Roon and redo it all for backups, etc., to run again.

I have very pitiful networking knowledge - I Googled it and opinions seem to vary between assigning the NAS a static IP, or setting up a DHCP reservation. Are either of these better than the other? Any issues I should be aware of before attempting either one?

TIA.

HC: 861v4/ID40/LPS, DSP5000, DSP5000VC, DSP3100, SW1600, HD621, Oppo BDP-105, Sony VPL-HW55ES
2-Channel: Oppo BDP-105, TEAC VRDS-7/Trichord Clock 3/PSU, 551, Quad 303, Harbeth Compact 7ES-3, Kimber cables, Russ Andrews mains and supports.
Previous Meridian: 5000C, 5200SL, 7200.2, 6000, 562V.2, 568.2mm, 800v4, 808.2i, 818v2/v3, 861v8, 502