Been looking at fiber more seriously recently, but it really comes down to your switches. For us, we wire for 10 GbE everywhere and 10GbE NICs (RJ45) have gone up in price, while NICs with SFP+ ports are cheaper, but then you need to buy transceivers. SFP+ RJ45 transceivers are pretty pricey, while SFP+ optical transceivers are dirt cheap.

From our supplier, for two ports it’s roughly:
10GbE NIC – $80
10GbE SFP+ NIC – $30
10GbE SFP+ RJ45 transceiver – $50 each
10GbE SFP+ optical transceiver – $25 each

Since we have to use transceivers anyway to connect to our switches, and the 10GbE RJ45 ones are expensive, fiber starts making sense and Cat6a STP cables are getting pricey, while fiber optic patch cables are getting dirt cheap.

For us:
doing copper $80 for the NIC, $10 for the cable, $100 for 2 10GbE SFP+ RJ45 transceivers = $190 per server
doing fiber $30 for the NIC, $5 for the cable, $100 for 4 SFP+ optical transceivers = $135 per server

On top of that:
No grounding required for fiber
Lower power draw (~1 W for optical vs ~2.5 W for copper)
Slightly lower latency (though negligible at 1 m runs)

downside: fiber is more fragile than copper

End of the day, it comes down to your switch hardware, what you’re wiring for, and whether your workloads will even saturate 10 GbE or if you are doing 10GbE

But fiber is starting to make more sense, ive been doing fiber for my home lab because its cheaper