It really depends on your perspective. If we’re talking about BTC or ETH, most likely it will be for long term without knowing when it will actually push through. The price movement is uncertain and unpredictable, so you may not know when will it happen and it can go up or down without warning.
In a bear market, this does not only apply to BTC or ETH, the same applies to all altcoins. Both of these coins have good prospects and there is not much difference which one you choose, I assume that in the end both will show approximately the same growth. But since I’m more inclined towards bitcoin, I personally buy bitcoin myself, and now there is practically no ETH in my portfolio, some very small part lies just in case, but my basis is bitcoin.
As a newbie, Bitcoin is still the best choice to start knowing more about crypto. I know altcoins could also have potential but we can't deny that there are a number of worthless altcoins and if ever we mistakenly invest with them, that $100 will surely turn to $0. That is why it was suggested to put our funds into a reliable project like Bitcoin because even if we hold them for 5 years or ten years, we gonna expect growth of its price which literally won't fail us and gives us profit.