What's more important to you?
Do a comparison here: http://www.virginmobileusa.com/shop/compare/#/lgoptimusf34glte/iphone48gbwhite/iphone4s16gbwhite/
The F3 is an Android phone which means you can download Android apps. It also uses the Sprint 4G LTE for data which is very fast. But 4G LTE is not available everywhere yet. It also uses the Sprint 3G network. Cannot create a mobile hotspot.
The Apple iPhone 4 lets you install iPhone apps. It uses the Sprint 3G network for data and web browsing. Not as fast as 4G LTE but the network is more widespread across the nation. Can optionally create a mobile hotspot to share web access with computers, iPods, laptops, and other phones.
► Before buying any 4G Beyond Talk phone you should check COVERAGE in your area on the top line of this webpage.
Follow the link at this FAQ: http://virginmobileusa.custhelp.com/app/answers/detail/a_id/5679
Be sure to select 4G LTE or 4G WiMAX on the tool above the map.
Hint: Click MANAGE MY ACCOUNT and sign up for Auto Pay to get a $5 per month discount on your Beyond Talk plan ONLY WITH an Apple iPhone from Virgin Mobile USA.