[nunez]

They are right.

Hotels will almost always match lowest rate because they care much more about having low vacancy and not having to pay booking.com for your reservation. And you won't sacrifice points or chances at upgrades.

Booking.com is a good way of finding low prices that hotels will match.

[what_ever]

Hotel aggregators are best places to find low prices not booking.com. It's possible that Expedia family of sites have better deals which you won't see on booking.com. So TripAdvisor and Trivago are better.

Disclosure: Used to work at TripAdvisor.