Which of the leading cryptocurrencies will become more scalable and efficient in the long term?
Will it be Bitcoin with its Layer Two solutions such as the Lightning Network and Sidechains?
Or Bitcoin Cash with its on-chain scaling solutions by increasing the block size limit?
I would like to know your thoughts about this.

The answer are obviously, of course it's bitcoin.
We know that bitcoin we used all the way and it's good through the transactions. But if you believe in onchain scaling are more important, you may choose bitcoin cash.