In the wake of T-Mobile's recently unveiled Simple Choice plans, Virgin Mobile is capitalizing on the shakeup by playing a value card of its own. Now through May 31st, the Sprint-owned MVNO is offering $100 credit to all T-Mobile subscribers willing to port their number to Virgin Mobile. Study the numbers for yourself and the deal seems a no-brainer, as Virgin matches T-Mobile's unlimited scheme with a monthly bill of only $55, which rings in $5 less than the UnCarrier's $60 (2.5GB) alternative. Naturally, that's where Virgin Mobile hopes the conversation ends, but we don't need to tell you that there's quite a difference in speed between Virgin's EV-DO / WiMAX service and the speedier HSPA+ / LTE alternative from T-Mobile. That said, if your inner cheapskate is tingling, you'll now find an extra $100 incentive to make the switch.