I tink that it will dpeend on your strategy.
But for me, I prefer to use pairing ETH/USD than /BTC. Because, using BTC pairing will be quite risky for me, moroever if I am willing to have it for long term. Inaddiiton, USD is more stable so we will know the upa nd dpwn price at least. In other hand, we also need to cosndier about the fee of traidng using the pairing. Sometimes, there will be some different rates or fees in some exchanges. But sometimes, it is lower or the same.