Bitcoin is better than bitcoin diamond because bitcoin is king of crypto currencies and it is a most promising coin. But I'm not interested investing in these two coin because now the price of bitcoin is very high and the growth of bitcoin diamond is very low. So I will not invest in these coins. But there are many good altcoins in the market. Ethereum , chainlink, uniswap and cardano are best coins to invest. You can try to invest in these coins.