Fun. If you want PCIe on a SBC without the soldering, I highly recommend perusing Hackerboards. I'm very happy with my RockPi 4 (4GB RAM, PCIe, USB 3, 6 cores), which I discovered through their excellent database.
The biggest factor though is support. Raspberry Pi has a lot of software support, so you aren't running into weird bugs here and there with nobody around to help. The Jetson community isn't nearly as big, but Nvidia's track record on their software support is generally quite good. In this case, they have an extra interest given their push for commercial applications and that the X1 sees use in the Nintendo Switch and Shield TV (among other things).
That being said, I missed the PCIe on the specs last time I was comparing SOCs and I had forgotten about hackerboards, thanks for the reminder!
Listed under Storage in the specs.
eg not a useful PCIe slot for anything other than plugging in an SSD
https://www.newegg.com/p/17Z-00AP-00018?Description=m.2%20ad...
PCIe support also allows M.2 cards to take advantage of the nonvolatile memory express (NVMe) protocol, which brings a large performance advantage over other types of interfaces due to reduced latency, increased IOPS and lower power consumption.
There's a whole parade of micro-computers that don't differentiate each other.