There is no clear answer, which is better, personal preference. For me, Ethereum is more attracting, especially now, that it looks much cheaper, than Bitcoin.
But bitcoin is safer because it has a large marketcaps and that means its users are very large and even exceed ethereum. bitcoin fluctuations are also not as big as ethereum. so it will be safer to invest in bitcoin. but that doesn't mean ethereum isn't good. This coin has great potential too. so I split my capital into several assets like ethereum and bitcoin