Technically Bitcoin Cash is better. bigger block size, faster transaction speed, low transaction fee and it is already trading over $800+
But Bitcoin has first-mover advantage, you can buy almost anything with Bitcoin core. From coffee to apartments and its return is much more than Bitcoin cash.
A better idea would be a 7030% investment in Bitcoin and Bitcoin cash respectively.
Also, if youll have Bitcoin then you are eligible for any free currency(like Bitcoin cash) comes out of any Bitcoin fork.