Re: Turning on Wireless turns off 3G ???
There's a hierarchy of data usage by the radios. If you're connected to wifi, the phone will always first pull data from the wifi. Not much of a surprise though, if Sprint can get you your data without using bandwidth on their servers, they will.
The hierarchy goes like this: Wifi>4G>3G (if you had all radios on). Turning on one doesn't "turn off" the others though. You have to manually turn them off, either in the settings or by using the widgets.
There is most definitely an advantage to manually turning off your 3G (mobile) radio if you're connected to wifi. Even if you are connected to a wifi network, the mobile radio will continue to poll and search for the Sprint network to keep a valid connection unless you turn off Mobile. The battery drain can be pretty significant.
I stay on wifi at home and idling for one hour I go down maybe a % or two with wifi on and mobile off. Away from home (in a place with a good solid signal) if I idle for an hour with 3G on and wifi off, I drop 5-8%.
Best suggestion, is to put the wifi/3G (mobile) widgets right next to each other and when you turn one on, turn the other off. There's really no reason to have both radio's pulling juice from the battery.
There are no stupid questions. Unless the answer to your question is "Earth".