Yeah its been known for a while. Its not any more an advantage this gen than it was last gen. You can hook up any external to an X1 or just use the unlimited cloud storage.
Fast out of the way internal beats hanging external (especially with front USB only) and Cloud any day IMO. But do consoles really need huge storage? If there were rear USB 3.0 ports, I "might" tend to agree with you, but in the living room, the less wires and boxes the better.
I'd rather see, with the more PC-like innards, better SSD support. The PS3 with SSD shows only modest improvement and no/trim, collection support.