The verdict

CPU
Dell OptiPlex 7080 Micro has 2.4x the CPU throughput (12,829 vs 5,307 PassMark).
Plex
Minisforum UN100L transcodes more 4K HDR streams (~5 vs ~3).
Idle power
Minisforum UN100L idles lower (8W vs 11W) - cheaper to run 24/7.
RAM ceiling
Dell OptiPlex 7080 Micro takes more RAM (64GB vs 16GB).

Which wins for each job

Job Dell OptiPlex 7080 Micro Minisforum UN100L
Plex / Jellyfin ~3 streams ~5 streams win
Frigate NVR ~4 cameras ~4 cameras
Proxmox / VMs 12,829 PassMark win 5,307 PassMark
Firewall / router 1 NICs 1 NICs
Local AI / LLM no slot no slot

Approximate - capacity estimates from curated specs, the same logic as the recommender. Verify against your exact setup. Prices move; check the retailer.

Full specs

Spec Dell OptiPlex 7080 Micro Minisforum UN100L
Price (list) $210 $199
CPU Intel Core i7-10700T Intel Processor N100
Cores / threads 8 4
PassMark 12,829 5,307
iGPU Intel UHD 630 Intel UHD (24 EU)
NICs 1 1
NIC model Intel I219-LM 1GbE (chip unlisted)
RAM max (GB) 64 16
M.2 free 0 1
PCIe slot none none
Idle (W) 11 8
TDP (W) 35 6