Best RF transmitter and receiver for Arduino - 433MHz, 2.4GHz or 868MHz?

Hello, what is the best transmitter and receiver to use with the Arduino to transmit sensor readings ?

I have already tested 433MHz and 2.4GHz,
Would something based on 868 MHz be better ?
I'm concerned about range and "purity" of transmission.

From which sensors ?
A lower frequency means fewer problems with the signal passing through the proverbial wall but more energy expenditure and greater susceptibility to interference.

Anything, the sensor can be for example a motion sensor. I need to send 2 states every 1 second or so.

So it would be better to use the 868 frequency ?
At the moment 2.4 GHz loses some packets of information.

There is no simple answer to the question of which frequency to choose. Different bands are used in home automation. Each has some advantages and disadvantages. It is up to the knowledge and experience of the designer to choose the optimum frequency for the application.
Note that some sensors consume very little current and are powered by a watch battery, for example. In this case, choosing the 2.4GHz band is a sensible solution. There will also be relatively little interference from outside in this band. The walls of the building strongly attenuate this range. As I have written before, a reduction in frequency means more current drawn by the transmitter/receiver, less attenuation of the signal by the walls but therefore also more interference from outside the building.