Consider Your Table Tennis Style
Probably the first thing to think about is the way that you are hoping to play. Different styles will have very different requirements for their table tennis rubbers. Think carefully about how you play both your forehand and backhand strokes - the chances are good that you don't hit the ball the same way on both sides. If this is true, you probably will want different rubbers that best suit your forehand and backhand. If your strokes are pretty similar on both sides, you can use the same rubber on both sides of the bat, of course.
As we discuss the various factors involved in choosing a table tennis rubber, keep in mind the way you play. This will help you to narrow down the list of possible rubbers suitable for you.
Although I will discuss the sponge and topsheets of a rubber separately, in most cases they are purchased together. For example, Sriver can typically be purchased with the same topsheet but with different sponge thicknesses such as 1.5mm, 1.9mm, 2.1mm and 2.5mm. These are all still called Sriver though.
Sponge
There are several things to consider when choosing your sponge. These include the sponge thickness, it's density or hardness, whether to buy it separately from the topsheet, and whether to use it at all!Sponge Thickness
The thickness of the sponge will affect how fast the overall rubber will be, and also how much control it has. Thicker sponge is faster but has less control than thinner sponge. Most attackers use sponge of 1.9mm or thicker, while many defenders (but not all!) use thinner sponge. Most professionals also like thicker sponges because they reglue the rubber each time they play, and the thicker sponges absorb more glue than thinner ones, increasing the so-called 'speed-glue' effect.
Sponge Hardness
Similarly to sponge thickness, the hardness of the sponge will have an effect as well. The harder the sponge, the less the ball will tend to sink into the sponge, and so the 'dwell time' will be reduced. This tends to mean that harder sponge will produce less spin than softer sponge. Whether this improves your control really depends more on the type of strokes you use - drivers and smashers tend to like the harder sponges, while loopers favour the softer sponges.
Buying Sponge Separately from the Topsheet
As in any sport, there are always those players who feel the need to tinker with their equipment, searching for that perfect combination of sponge and topsheet. If you are one of these players, feel free to try different combinations of sponges and topsheets - be aware that not all combinations are necessarily legal in competition though! For the majority of players, it is easier and better to simply stick to buying the usual rubbers that have the sponge and topsheet already joined together.
No Sponge
It is possible to not use sponge at all - however this means that you must be using a pimple-out rubber. It's not legal to use an inverted, or smooth, rubber without sponge. Using no sponge can be an effective tactic for those players who defend or twiddle their bats.
