When investing, Im a big fan of diversification of portfolios. I believe that both Ethereum and Bitcoin offer value, albeit in different ways.
Even though Ethereum is positioning itself to become a large platform, the fact that Bitcoin is so well known makes it the first place where people invest.
Since you believe in both. Why don't you keep both. You knew that they have a good platform and aim to become the best. So better to keep both and keep buying. Both are really good for long term investment.