You are still overpaying when using Amex/Chase/Cap1 portals.
$105-110 book on Amex/chase/cap1 portal
$101-102 after 5-8% travel portal cash back
versus
$100 book direct Hilton/marriott/IHG rate
$96-97 after 3-4% cash back everything card.
Don’t even get me started on “premium programs” like Amex FHR, Chase Edit, etc. Probably overpaying by $100+/night. Much cheaper to just pay for 4 pm checkout. And early check-in is dead anyway.
This hasn't been my experience. I usually search through Booking.com and when I contacted the hotel directly, found that the direct rate is higher than the booking.com rate.