if I were you I would choose which one is greater in value
for example, as you said at the beginning of buying ETH at a price of 0.03 BTC or around 300 USD then at this time the price of BTC went up so that the price of BTC against ETH would decrease for example to 0.02 or around 500 USD
You must be confused if you have to choose to change it to BTC or USD
the wrong choice is to change it to USD instead of BTC because if I change it to BTC then I lose because my initial investment is 0.03 BTC and if I change it now what I get is 0.02 BTC or a loss of 0.01 BTC then I change it to USD where the initial investment value is 300 USD and now it has become 500 USD