EFD Software's HD Tune is described on the company's web site as such: "HD Tune is a hard disk utility with many functions. It can be used to measure the drive's performance, scan for errors, check the health status (S.M.A.R.T.), securely erase all data and much more." The latest version of the benchmark added temperature statistics and improved support for SSDs, among a few other updates and fixes.
The Samsung X5 Thunderbolt 3 Portable SSD
put up the best sequential transfers here as well, and its read latency was the best of the group too. However, its write latency trailed some of the internal drives, which isn't surprising considering the overhead associated with its external interface.