For what it's worth, I have both a SATA-based Samsung portable SSD and a NVMe-based SanDisk portable SSD, and they've both been almost completely trouble-free f

For what it's worth, I have both a SATA-based Samsung portable SSD and a NVMe-based SanDisk portable SSD, and they've both been almost completely trouble-free for me—though I am careful in how I use them. I'm definitely not the disgruntled customer you seem to think I am (especially because both of those drives were review samples). For the smaller USB-native flash drives, I have not noticed any particular pattern to their unreliability, but I trust them even less because that product segment is a dumping grounds for low-grade flash memory. For NVMe-based portable SSDs in particular, I am wary in part because of the long-running thread on the AnandTech forums documenting how all three suppliers of NVMe to USB bridge chips (JMicron, Realtek, ASMedia) have had extensive problems with both reliability and compatibility. Companies like Samsung and SanDisk can certainly be expected to do more QA on their products incorporating those chips than smaller brands, but that's not a guarantee that they'll avoid the problems from their upstream supplier.