friends. imagne that there are 10 or 20 arduino device at a room. And you have an android phone and when you enter to that room , your android device connect to all of working arduino devices from number 1 to 5 or 19 or 20 only working devices and get data from them. So best way with wifi or bluetooth? And i want to do it with only one button click. I need your advices.
I think it would be faster (for the user) to use wifi because bluetooth will probably require a discovery scan every time you enter the room. With wifi you could UDP broadcast the ID of each device & show a list to the user to select from. You'd still have to listen for the UDP broadcasts, but I think it would be much quicker than doing a bluetooth discovery scan.
One minor point - I don't think that with either bluetooth or wifi you will be able to connect to multiple devices simultaneously.