Actually you can hit only aggressively or consistently. Trying to make your opponent to draw an error is an aggressive play. Hitting hard trying to make the opponent hit a short ball is an aggressive play. Hitting consistently is a defensive play, cause you rely on your opponent to draw an error.
The truth however is that there are different degrees of consistency and aggressiveness. Some shots that might be considered defensive might actually be very aggressive versus some players. For example, a slice can be called a defensive shot but versus someone that can't time his shots well it can be his nightmare. Trying to find the right mixture of consistency and aggressiveness in your shots is key, the flatter and harder you hit the ball, the more likely you are to draw an error or "win" the point. The more you force topspin to the ball making it go in. Many people don't understand that hitting consistently doesn't mean you have to push the ball or hit slower. All you need to do is hit the ball more upwards, creating that topspin needed.
Shortly, if your win more points of by hitting every ball in, go for it, because that way you are surely going to win. If instead your opponent has you on the run and you're all the balls in strategy isn't working, then you need to start being more aggressive. As I told you, being aggressive doesn't mean you have to hit ball hard. Hit wide angles, hit with different spins and get to the net.
