Anyone know why MX204 has so few ports? It seems like it only has WAN side used, leaving FAB side entirely unused, throwing away 50% of free capacity.
The usable port configs are also quite tricky. Juniper have had to make a tool to validate the configurations (https://apps.juniper.net/home/port-checker/). For example, using 4x40G disables all of the 10G ports however using 3x40G and 1x100G gives you all of the 10G ports
MX80/MX104 have both sides for revenue ports.
They are, however, not Trio - rather just commodity CPUs. Routing re-convergence times are shockingly high - in the region of 5-10 minutes for MX80 with a full table vs 30 seconds (ish) for 204
I would GLADLY take 50% more ports in MX204, without taking any more PPS or QoS bandwidth.
You can add switches (EX or QFX) as line cards using Fusion, to add more port density. I've heard some good things about Fusion, though I'm always wary of proprietary clustering technology having been bitten by VC a few times. You can also just trunk some VLANs up to switches if you don't want to buy the Fusion license