Classic and Core, both of them are good. If you are using Core, you should stick to it. Thats what i recommend.
In the long Run, both will be equally better and important.
in the long run both will adhere to the same protocol (what ever that happens to be 2MB blocks or segwit-ed blocks).
there will be no forking off.
If both of them are same in the future, would it will be better to combine the feature of both .
Means both of them using the same protocol and same block size.
It will be better.