It really much depends on the individual case. In a constitutional state it should make a difference if obviously an encrypted volume is used or if there is the possibility but no certainty of one, two, three or four hidden volumes.
I think this can be better explained by starting with the company (instead of the device) which is lean but still requires development and maintenance, purchasing and manufacturing, billing and accounting, customer support, management, shipment and logistics. Those tasks need to be paid.
Plausible deniability refers to Nitrokey Storage's hidden volumes. They can optionally be setup, but no need to, and without the appropriate password it can't be distinguished. Similiar to VeraCrypt's hidden volumes.
Measured boot allows to verify the integrity of the installed firmware (which itself verifies the integrity of the Linux boot partition) by a separate Nitrokey. The idea is that you have your Nitrokey nearby and therefore safe against compromise, other than the laptop which may be left unattended.
I understand OpenSSH is going to support the FIDO U2F standard in which case all standard-conform implementations would work, including Nitrokey FIDO U2F devices.
I understand OpenSSH is going to support the FIDO U2F standard in which case all standard-conform implementations would work, including Nitrokey FIDO U2F devices.
I try to minimize complexity and ideally use a single key for all clients, projects etc. This works well for SSH and reasonable well for PGP. I store my key on a Nitrokey Pro secure USB key so that I can carry it with me and safely use it in any environment. This way I don't have to use separate keys even from the security perspective.
Yes, a Nitrokey with OpenPGP Card and FIDO is planned. You can get notified directly by subscribing its newsletter at https://www.nitrokey.com/newsletter
From the security point of view the most obvious difference to me is that Nitrokey contains a secure element while Secalot doesn't. (Secalot contains a microprocessor with cryptographic acceleration but don't confuse this with a secure element.) Secure elements are secure key stores which protect against extraction of cryptographic keys by malware and by physical attackers.
Also Secalot seems to be a small project while Nitrokey is a (small) company, which might influence quality of security and maintenance too.