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Thunderbolt 3 provides the most bandwidth for storage devices
If you use Thunderbolt Connectivity for Storage devices, stick with Thunderbolt 3.
Thunderbolt 4 is shiny and new, but is actually slower for storage related applications.
While it is true that Thunderbolt 4 controllers are capable of providing up to 3 Thunderbolt downlink ports (as opposed to 1 for Thunderbolt 3), this comes at a cost. The PCIe 3.0 bandwidth is limited to x1, versus x4 for Thunderbolt 3.
In other words, Thunderbolt 4 will provide more connections, but will limit storage devices to PCIe 3.0 x1 speeds (985MB/s, MAX). By storage device we mean any drive; HDD, SSD, RAID array or enclosure, of any interface type (USB, NVMe, SAS, SATA).
HighPoint Thunderbolt 3 products, such as the RocketStor 6661A PCIe Expansion chassis and RocketStor 6662A Hardware RAID Enclosure, require x4 lanes to perform optimally. These devices are capable of delivering up to 2800MB/s of transfer performance using a Thunderbolt 3 connection.
The Takeaway:
If you use Thunderbolt for storage, we recommend Thunderbolt 3 connectivity. It is able to allocate 400% more transfer bandwidth for storage devices.
If you work primarily with video devices, or need general-use connectivity for large arrays of USB peripherals, Thunderbolt 4 may be a better option. However, it limits storage devices to PCIe 3.0x1 speeds.