The verdict

CPU
Beelink SER9 has 1.1x the CPU throughput (34,991 vs 31,519 PassMark).
Idle power
Beelink SER9 idles lower (8W vs 15W) - cheaper to run 24/7.
Networking
Minisforum MS-A1 has more NICs (2 vs 1) - better for a firewall or VLAN trunk.
RAM ceiling
Minisforum MS-A1 takes more RAM (96GB vs 32GB).

Which wins for each job

Job Beelink SER9 Minisforum MS-A1
Plex / Jellyfin ~5 streams ~5 streams
Frigate NVR add a detector add a detector
Proxmox / VMs 34,991 PassMark win 31,519 PassMark
Firewall / router 1 NICs 2 NICs win
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 Beelink SER9 Minisforum MS-A1
Price (list) $999 $259
CPU AMD Ryzen AI 9 HX 370 AMD Ryzen 7 8700G
Cores / threads 12 8
PassMark 34,991 31,519
iGPU Radeon 890M (RDNA3.5) Radeon 780M (RDNA3)
NICs 1 2
NIC model Intel I226-V Realtek RTL8125
RAM max (GB) 32 96
M.2 free 1 1
PCIe slot none none
Idle (W) 8 15
TDP (W) 65 65