I dont think thats true.
All of my games are installed on the external HDD (the xbox one makes that your default unless you select otherwise I think) and all load faster now.
In theory, they should be pretty close. But in practice USB 3.0 has been shown to be a good bit slower than SATA III. Not really sure why...maybe there is just extra overhead with USB 3.0? Though I have heard that many USB 3.0 ports don't actually run at full speed.
Bet with Adamblaziken:
I bet that on launch the Nintendo Switch will have no built in in-game voice chat. He bets that it will. The winner gets six months of avatar control over the other user.