It might become a comparison with the Pi4 compute module + the current breakout board they are offering which has a PCIE 1x slot. So far some NVME drives are confirmed to work. Keep an eye on Jeff's channel[0] as he's even poked around at getting a GPU working as well. But he's having some issues atm (personally I believe he needs a breakout board with more power output).
Here's a fresh submission to HN on hooking up a 4-port gigabit ethernet card[1] to the Pi Compute Module 4.
Throughput is coming. I look forward to 2026 or so when I expect things like PCIe over Thunderbolt to start becoming more semi-standard, integrated on to more and more SoC. Already, a TB4 port can do 80Gbps of DisplayPort connectivity. With that kind of oomph, it makes sense to also start considering how we might also use those same transcievers & cables to do more data-oriented tasks.
[0]https://www.youtube.com/watch?v=vc_Lh_a1BQI