I prefer on bitcoin because it has a higher value that Ethereum in which you can easily have much money. Particularly bitcoin is not just an easy to get but if you're hard working and patience people it's worth the wait day by day the price of bitcoin is getting higher and higher.
if i had to choose on bitcoin vs etherium then id go on both of them because both of them are quite good and verry profitable among other coins out there. both of them are also has advantage and disadvantage like for example bitcoin is highly volatile coin but unstable while on the other hand etherium is less volatile but more stable. both of them also has an important usage, etherium can be used when trading your other tokens and altcoins while bitcoin can be used when buying online or offline.