Well buying is a bad idea - people should have done that before all the hype about the ETF coming soon which has dramatically pushed up the price. You should only but if you're very optimistic about the ETF or you're prepared to hold for a long time.
I have mixed feelings on this. You could still buy right now since the ETF hype is still affecting the price. It's only gone down for now due to the issues with the Chinese exchanges. Soon the hype will take over the price again since we're nearing March 13. You could still make a profit regardless of the ETF results. If it's rejected, you just have to be quick to sell before the dump.
Selling could have been a good idea recently - it was clear for a while that it was staying near $1300 before it then fell down to around $1200. If you were clever enough to notice that temporary climax you could have sold then and bought again about now.
This, I agree on. Personally I missed the peak though, but I'm hoping for the price to get near $1300 before the ETF decision.
In my view, there's an option missing here, which is trading. If you're clever enough then during this time of volatility you could earn some decent money by buying and selling repeatedly in ways which earn profit.
For the less experienced in the market like me, the best option is to hold because I know that eventually Bitcoin is going to rise much higher. It could well take a year before the network issues are sorted out and it becomes good enough, but that's okay because there's no point making a rash decision to sell during this (probably temporary) high.
If you really believe that bitcoin will rise, then if you have cash right now, buying won't be a problem. But if you're satisfied with your stash, holding is definitely the best option.
Personally, I plan to wait for the ETF decision. If it's approved, I'll buy more and ride the succeeding pump. If it's rejected, I'll sell my short-term stash and wait for the dump before buying more. The issue with the Chinese exchanges and the current price admittedly caught me off guard. But if I won't be able to sell my short-term stash at a profit, I'm fine with holding.