The verdict

CPU
Beelink GTR9 has 1.6x the CPU throughput (54,968 vs 34,991 PassMark).
Idle power
Beelink SER9 idles lower (8W vs 16W) - cheaper to run 24/7.
Networking
Beelink GTR9 has more NICs (2 vs 1) - better for a firewall or VLAN trunk.
RAM ceiling
Beelink GTR9 takes more RAM (128GB vs 32GB).

Which wins for each job

Job Beelink GTR9 Beelink SER9
Plex / Jellyfin ~5 streams ~5 streams
Frigate NVR add a detector add a detector
Proxmox / VMs 54,968 PassMark win 34,991 PassMark
Firewall / router 2 NICs win 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 Beelink GTR9 Beelink SER9
Price (list) $1,985 $999
CPU AMD Ryzen AI Max+ 395 AMD Ryzen AI 9 HX 370
Cores / threads 16 12
PassMark 54,968 34,991
iGPU Radeon 8060S (RDNA3.5) Radeon 890M (RDNA3.5)
NICs 2 1
NIC model Dual 10GbE Intel I226-V
RAM max (GB) 128 32
M.2 free 1 1
PCIe slot none none
Idle (W) 16 8
TDP (W) 140 65