On the 360, you have a roster just like the One. Let's say you have 3 full pages of friends playing destiny. 1 page = 12 friends, that's 36 friends online playing Destiny.
Now, you can inspect every friend on Destiny AND compare weapons for every single friend playing Destiny. Accessing 14 different items from each friend and comparing to your own. That's the potential of accessing 504 items and comparing to your own.
That's way more than what's in your vault. A paging mechanism would solve the vault issues. And I've just shown its possible through the old-gen.