Dear OP.
Few steps to answer this question:
* Go coinmarketcap.com and check BTC vs ETH vs ALTs performance in marketcap volume.
* Go to tradingview.com and open yourself a chart of ETH vs BTC and look at the prices change.
Result?
BTC winning vs. ETH for about 45% this year alone - price wise
BTC winning vs everything on market cap. This year BTC went from 31% to 45%
So now you see BTC winning, however you feel like ETH could break out at some point and start gaining vs BTC? Okay good, we must all keep that option open and embrace it if it happens and mostly we must use it to our advantage. Therefore, untill BTC is winning the game keep your $$$ in BTC and simply monitor the market. If or when it happens trade 50% of it into ETH and profit.
Conclusion?
Knowledge is everything. Learn from the past charts, gatther info and adapt.
BR