The LG Optimus F3 doesn't make much sense on Sprint, where a preference for contract pricing leaves the F3 competing with more advanced devices. It's a good thing that the 4-inch Android phone has launched on Sprint's contract-free Virgin Mobile brand, then. The smaller carrier's version offers everything we've seen before, including LTE, but costs just $180 up front -- a big discount over both the $250 Sprint variant and most 4G phones at Virgin. Combined with cheaper plans, Virgin's Optimus F3 should be a much better deal for those who want LTE on the cheap.