J.K.
If you're even talking about the possibility of reversal, sounds like you're not ready to close the door. Vasectomy reversals are expensive, most likely not covered by insurance, and the success rate is only around 50% I think. Tubals are more invasive. If you're having these thoughts, I think you should wait on this more permanent form of birth control.
With Mirena, it's not known exactly how it works. There is the possibility that the egg gets fertilized but isn't allowed to implant. Since for me I believe that life begins at conception, I couldn't do Mirena.