Besides what you're referring to, remember there are cards that earn extra points for booking a certain way, even if it's not through a portal.
Many airline cards earn extra miles / points for booking directly through that airline. Some even give an annual cash credit of some sort when doing such a booking (on top of the extra miles / points).
There are Amex cards which earn extra MR points for booking directly through any airline.
And of course there are cards that earn extra points for Travel which can include airlines (probably booked multiple ways, depending on the details of the travel bonus points benefit).
Meanwhile, to different people different points / miles have different value. So a card giving extra points of a certain type may or may not be as valuable to a given person as another card that doesn't give extra points of a different type.
So once you get the "travel portal" information, someone will have to compare the "travel portal" bonus to all that above to see which works better for a given person in a given situation.