It's best to diversify your investments, 50/50 would be a good split if you want to also have a chunk of the etherum cake and bitcoin as well. Etherum, while alot of people would rather pick bitcoin and understandably so, is also an promising cryptocurrency, it may earn you some money too and who knows, maybe it'll become stronger in the future?
Just like bitcoin other crypto currency I mean altcoins will have bright future (depends on development and adaptability) so it's better to invest in altcoins as well with a proper research.