Which is "the real" Bitcoin per the original ideas and hence valid chain, is not necessarily the same as which is "the real" in terms of being the current PoW majority chain in terms out of the forks resulting from the split. I suggest you try out both.

If you've been in crypto any lenght of time and have some Bitcoin SL "Core" (still using ticker BTC) you may also check if you have some Bitcoin Cash tied to your address.