Directional tyres normally have better wet weather grip than non directional tyres, the tread pattern is designed to clear water from from underneath the tyre and reduces the risk of aquaplaning on very wet roads. As your rear wheels normally follow the front wheels directional tyres clear water from the path of the rear tyres so that improves the rear end grip, but remember that no tyre can cope with deep standing water so in really heavy rain you should always reduce your speed.

I often get asked for a left and right tyre and sometimes customers ask for a pair of left or right tyres, all directional tyres are identical and can be fitted to either side of the car , it's the way that they are fitted to the wheel that determine which side of the car they will be fitted too.