Stay those ETH as they are and let it idle for long term holding purposes.

What you must do is to get another bunch of your extras ammos right from your pocket to buy bitcoin at the current rate or if by means that you have no chance of buying it directly with the thing I mentioned then earned it by doing any kinds of method. If you really believes that bitcoin will make again another big price increase then do it now before regretting later.

Holding them both are good. Pros and cons? Price volatility and that's it.

This is only based on my own view if Im the person involved in your case and not suggesting you to follow it. Follow your heart this is your investment after all. Goodluck.