RANSAC is an abbreviation for "RANdom SAmple Consensus". That said, we must expect the output matrix to change as the samples are randomly picked.
In OpenCV, the values are picked from a uniformly distributed list of random values. Thus we get the same values every time we run the code.
In Matlab, it that seems to pick a completely random value and hence the problem. You will have to check whether there is a way to random-seed the picking of random values, which I am quiet unsure of.