I only use two apps, but that's because I stay in hotels or pensions - I don't stay in AirBnB or other private accomodations.

TripAdvisor - I find this app useful for determining what hotel / motel / pension sites are available in a neighborhood or city, what the going rates are, and to read reviews posted by others about these facilities. My experience has been that the prices quoted by TripAdvisor are generally accurate.

Booking.com - This is my "second choice" app if I don't find what I am looking for on TripAdvisor. My experience has been that Booking.com often lists inaccurately low prices when you look facilities up, and then if you go to make a booking (either via the app or by calling the facility), the real prices are considerably higher. So for me, Booking.com is a fallback option only.

I use these two apps for research, but I don't make the actual booking through the apps. I call the facility directly and ask them what they have available and what the cost is. Often, the price asked when dealing directly with the facility is less than what is shown on either of the two apps. If the facility quotes a higher price than what the app shows, I tell them that the app is showing a lower price and ask if they would like me to book through the app. Always, the facility will offer to match the app price because they don't want to pay the 15% (or more) commission to the company that runs the app.

Michael