Hello miss, BTC is caped to 21millions top, ETH is unknown by the moment, more than 100millions of ETH on circulation by now, so basically BTC is more scarce than ETH, offcourse ETH offers a lot of use cases better than bitcoin, but ethereum is still under development, bitcoin is at production level now, work as store of value and nothing more, it have the longest chain alive so people trust more on BTC than ethereum. At least this is from my poing of view.
If you have any more questions, please let us know so we can help you!
Carlos Z.