I like what Nitrokey is doing. If auditability is the most important requirement then it seems the better option. On the other hand, the capacity is limited and the speed is only USB 2.0 (c.f. the Apricorn Aegis devices which are all, I think, USB 3.x - and quote actual read/write speeds).
I think I’ll wait until I receive the Librem 5 before moving on to my next imported gadget. 