Recently we analyzed the Hardkernel offer in light of OpenSecurityTraining2, and it looks pretty good but is more expensive than UP2. For example, the UP Squared Pro 7000 Series [1] is fascinating.
The pros of Hardkernel are open schematics (same as PC Engines), which is crucial if one would like to have open-source firmware like coreboot. Quite good testing documentation, transparency, and community. UP2 does not provide schematics, and their support could be better, which can be proven by reading their forums. There needs to be a sense of transparency and community building for UP2.
Of course, UP2 and Hardkernel products have other drawbacks compared to PC Engines, namely, no D-RTM, fewer NICs, higher TDP, no ECC, etc.
The pros of Hardkernel are open schematics (same as PC Engines), which is crucial if one would like to have open-source firmware like coreboot. Quite good testing documentation, transparency, and community. UP2 does not provide schematics, and their support could be better, which can be proven by reading their forums. There needs to be a sense of transparency and community building for UP2.
Of course, UP2 and Hardkernel products have other drawbacks compared to PC Engines, namely, no D-RTM, fewer NICs, higher TDP, no ECC, etc.
[1]: https://up-shop.org/ups-pro-7000-series.html