Booking.com and Expedia charge hotels 15-25% commission. For boutique hotels especially, this affects the rates and rooms you get. Booking direct often produces better outcomes: same or lower price, better room allocation, more flexibility, sometimes perks.
The compare-then-call tactic
Find candidate hotel on Booking.com. Note the price. Go to hotel's own website. Compare. Often direct is the same or slightly cheaper. If aggregator is cheaper, email or call hotel: 'I see Booking.com is offering this rate; can you match or beat it?' Many will, plus add free breakfast or upgrade.
Where aggregators still win
Chain hotels with loyalty programs that match across booking channels. Last-minute when direct sites haven't updated. Cancellation flexibility (aggregators often offer free cancellation when direct booking doesn't).
Five extra minutes per hotel booking saves real money over time. Make it a habit for any non-chain accommodation.