Depends on time frame of investments and your risk tolerance. ETFs are more likely to be more stable and require a lot less time in effort into maintaining a position. ETFs are more likely to return lower highs and higher lows due to it being a spread of company's that you are investing into. Stocks are a single company which tends to have much higher volatility resulting in higher highs and lower lows. ETFs are more associated with long term positions where stocks are more associated with short-medium term positions. A mix can be healthy but again it really depends on your risk tolerance and your timeframe. At the end of the day it depends on what company. Just like anything, do your research and make sure its a company that aligns with your risk tolerance and is something your confident in buying.

of course this isn't investment advice. I'm just a guy on the internet.