Bitcoin is the leading cryptocurrency so if you want to invest on then you can really go invest bitcoin since its price is low as of now. Ethereum in the other hand is one of the leading altcoin although it is not the same price as bitcoin but it is still beneficial and more people invest on to this coin for it has a possibility to increase its price just like bitcoin. If you want to invest you can invest in both so you have more chances to earn a lot of profit.