A lighter spring will allow the slide to work faster, will have less muzzle flip, will get back on target faster and have less felt recoil. Some prefer all OEM parts. If you need more details about Glocks in general you can send me a PM.
Be careful about the light recoil spring. Too light, and the striker spring could pull the slide out of battery.If it fires out of battery,you will most likely be in search of a new Glock. If you must, be sure to compensate with the correct striker spring.
Too heavy a recoil spring will not let the slide cycle as intended. And your Glock will not work properly,or at all.