Phase Difference Between Two Signals (Problem)
Both of the results you got are right. You feel it confusing, because you imagine it as a running race, where one has to be first and the other the second, but in fact these are periodic signals. Which means that the leading is always relative. 

Try to sketch the signals and select a local maximum of i1. The i1 leads i2 by the distance between your chosen i1 maximum and the closest i2 maximum to the left. But there is another i2 maximum to the right from the chosen i1 maximum, so i2 leads i1 by that distance. Its always true that if you add these two phase differences, you always get 360 degrees, what you can use to check your answer