Well, I think ETH is the best choice, it is more decentralized among the three. BitMEX once said that Ripple is way more centralized than being a decentralized. And even some blockchain experts and enthusiast, doubted that even DASH is not-so decentralized one. So, I would love to choose Ether.
Well ripple isnt exactly centralized. I agree that still most of the supply of XRP tokens is held by the ripple company itself, but there is a legal limit or restriction to the number of tokens the company can sell or release each month to fund their projects, etc.
Soon ripple will be wholly decentralized after the whole supply is released in the market. Anyways in terms of security I would agree that ETH is better, but as an investment I would go with XRP in the long run.