Is it better to use DRIP or invest when stock drops before ex-date?
The benefit of a dividend reinvestment program is you, generally, don't pay transaction costs or commissions and you don't have to remember to do it.  Whether or not you may be able to eek out a little more by managing this yourself is a crapshoot and the equivalent of timing the market.   If you're so good at timing the market you shouldn't even be holding the stock, you should be buying and selling as the price fluctuates.