The recent bitcoin price volatility is particularly large, but the price of ETH has been very stable, you choose to buy ETH or bitcoin?
The best strategy is to hold both.
If you are asking about right now then i think it is personal choice but both have good potential for big moves that can be confirmed by historical patterns.
If you ask about my personal choice i will vote for ethereum because it has bigger potential for growth than btc in my oponion.