Now the official hard fork has begun and the speculation of the future of bitcoin begins, should you invest in bitcoin or bitcoin cash. Personally due to the long term trust and over 8 year functionality of Bitcoin I think It's safest there. It's the first ever cryptocurrency and initiated the whole digital currency era that's currently worth over $90 Billion.
However, cryptocurrency being a very volatile market who's to say that Bitcoin Cash (BCC) won't rocket to a sky high price, equaling if not surpassing the value of bitcoin. Maybe not realistic in the near future but who knows, I doubt many people thought the value of Bitcoin would reach what it has today, let alone its value continuing to rise.
All in all it's entirely up to you, the industry's still very fresh with new coins being developed and released everyday. Bitcoin started all this but 9 years later, is Bitcoin Cash its indefinite legacy or experimental failure, who knows.
Invest wisely.