In one sense, Maurillo, there is no difference!
Mammillaria albilanata ssp. oaxacana is a name created by Dr David Hunt in 1998 to bring together the previously described species of M. ignota, M. lanigera, M. lanigera v juxtlahuacensis, M. montensis and M. noureddiniana.
Initially Hunt used it to replace M. ignota and made all the others synonomous with it. There is no doubt in my mind that M. albilanata is a very variable species, and in some areas, Oaxaca certainly being one, the differences between the forms found there are relatively small, and in places they overlap and merge.