First of all S1 Suppressor does not lower your recoil. S1 only changes your recoil pattern. Great if you don't like a gun only knocking upwards, adding an S1 Suppressor can change it to going diagonal.
S2 Suppressor only masks the Gun tracer , or the bright bullet you see when you fire or an opponent fires. This suppressor is better for those that do not want to be seen when firing at enemies far away. Also , let's say you're stalking an enemy ... and you are behind them. You fire a bullet but miss , the opponent may clearly see a gun tracer past by them revealing your location. An S2 Suppressor would be great for this situation.
S3 Suppressor completely removes the Muzzle flash , or the bright diamond-like flash you see when you fire a bullet. This is great for situations when firing at medium range cause your enemies may think that you are not the one attacking them.
All of them have their advantage, you choose.