verizon iphone4: if it has access to wifi and 3G which will it use and what's best for battery life
iPhones will always use a wireless connection if one is available (and it is authorised to use it).  It will then use 3G (EV-DO).  And then 1xRTT as a last resort.  So it always prioritises wireless if available.

Wireless is generally better on battery life too.