This question refers specifically to the use of external 2.5" drives, spinning or ssd.
External drives on usb hubs we all know are very flaky, even for powered hubs.
Surprised I couldn't find an existing answer to this question. Quoting experience is one thing, but a technical reason why usb hubs are unreliable and why thunderbolt is better (if it indeed is for this use case) would be excellent.
It's a thunderbolt 2 dock I'd be looking to get, for a 2015 mbp, if that helps.