I am in the market for a new external drive to use with my MBP and FCP. I have been using a WD USB 3.0 but I want to upgrade to TB. What is a good one. I want at least 2TB but I prefer 4TB. I looked at a WD 4TB portable that has the integrated cable and you can use it as RAID or straight for $349 on Amazon. The downside to it is yes the cable is integrated so if the cable goes bad the drive is bad. Also from what I have read, there is a fan inside the unit and it is somewhat loud.
Looks like you are talking about a single hdd in an external enclosure. You will not gain any speed by switching from USB3 to Thunderbolt. A single drive will not saturate a USB3 I/O port. Even a single ssd drive that is 4X faster than hdd will not saturate a USB3 bus. Save your money.
Only by using a multi-drive RAID 0 will you ever saturate a USB3 bus.
If your hdd is a 5400rpm drive, then switching to a 7200rpm drive will gain you some speed.
You should calculate the maximum amount of data bandwidth you need and configure your system to that.