hi, please share your knowledge about which Arduino board is best for making Quadcopters and Drones.
There are many options (uno and mega not one of them).
A quick Google on “arduino drone project” would give you lots of ideas. Did you check that out?
yes, i have searched but all they tell me is how to make it. no one explains why they choose this Arduino model not others.
Could you provide the link to it? I would like to make complain to the internet commission of unexplained projects, this is outrage!
Does this help OP?
You would need a light, fast board (so indeed not uno or mega).
Perhaps you want to control your drone with BLE?
In that case there are boards that have BLE on-board.
If you want RF communication, you do not want the BLE on board (as it will add weight).
The Arduino shop has several options. To be honest, I cannot tell you which is the best.
What control voltage will your motors use? There is 5V and 3V boards. You would not want a level shift board needed...
If you plan to get your program from some tutorial, it might be a good idea to buy the same board. Arduino programs are not portable from one board to another (as pin layout and internal registers are different from board to board and from chip to chip).
Good luck!
Most of the time it is likely what they had in the drawer 
You’ll find projects with a UNO or MEGA.
The choice comes from the feature set you want to offer (GPS, FPV, face recognition or tracking,…) which will require more or less compute power capabilities hence impact chip and memory choice. A basic design will work fine with a 328P, an MPU, a radio and motor controller
Then you have other requirements, like minimum weight or size (that’s sheer a uno or mega are not optimized) for example.
You could also have a look at https://ardupilot.org/