Every stream in which you apply is reliable, if you fulfill all requirements of that stream. Among other requirements of the Provincial Nominee Programs, one is to show intention to live permanently in that Province which nominates you. So if you apply for MPNP, the visa officer will see that there is a likelihood that you will move to Alberta after getting your PR through MPNP as your real sister is living there. So IO would feel reluctant while approving your case for Manitoba nomination. I have seen a case where Manitoba refused nomination because applicant,s close relatives were living in Toronto and the reason was that your ties are stronger with Toronto then Manitoba.
So it is better that you apply for both Provinces at the same time and after approval from one, withdraw your 2nd application.
So it is better that you apply for both Provinces at the same time and after approval from one, withdraw your 2nd application.