>>96345017
I don't really have anything against B/X, I used to play it a fair bit, but I feel it starts to strain a bit at the seams around level 4-5 and you start needing to steal heavily from 1E or other sources to get it to run after that and let the players have enough magic items and to go on more spectacular otherplanar adventures.
Personally I figured at that point I might as well run AD&D. (OD&D meanwhile is sort of built for the kind of people who want to do that from the beginning and the spells are more powerful and vague from the start)
The reason I said not OSE isn't because of the system itself but more because it doesn't have all the good beginners explanations and advice you find in actual original Moldvay B/X so you can be really mislead by the OSE core books.