The verdict

CPU
Minisforum MS-A2 has 1.5x the CPU throughput (54,042 vs 34,991 PassMark).
Idle power
Beelink SER9 idles lower (8W vs 25W) - cheaper to run 24/7.
Networking
Minisforum MS-A2 has more NICs (4 vs 1) - better for a firewall or VLAN trunk.
RAM ceiling
Minisforum MS-A2 takes more RAM (96GB vs 32GB).
Local AI
Minisforum MS-A2 has a PCIe slot for a low-profile GPU - the other needs a DIY build for local LLMs.

Which wins for each job

Job Beelink SER9 Minisforum MS-A2
Plex / Jellyfin ~5 streams ~5 streams
Frigate NVR add a detector add a detector
Proxmox / VMs 34,991 PassMark 54,042 PassMark win
Firewall / router 1 NICs 4 NICs win
Local AI / LLM no slot PCIe GPU slot win

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-A2
Price (list) $999 $639
CPU AMD Ryzen AI 9 HX 370 AMD Ryzen 9 7945HX
Cores / threads 12 16
PassMark 34,991 54,042
iGPU Radeon 890M (RDNA3.5) Radeon 610M (RDNA2)
NICs 1 4
NIC model Intel I226-V Intel X710 (10G SFP+)
RAM max (GB) 32 96
M.2 free 1 1
PCIe slot none x16
Idle (W) 8 25
TDP (W) 65 55