Smashing a short high backspin shot

I often get into a position whereby my opponent has made a mistake and returned the ball back high (say very high) and short but with backspin.

I feel (and so do they) that this ought to be an easy kill but I seem to put it in the net way way too often.

Should I slap it down or should I brush it down?  Am I too late or maybe I should wait till it drops a bit?

Hi Dan,

Take a look at these video responses to a similar question:

High backspin close to net

Smash/Topspin High Chopped Ball