professor_chaosWell, OP, 3L is more waterproof. It means 3 layer and 2L is two layer
Not always. You could have a 20k 2l and a 20k 3l and they would be the same level of water proofness. The 2l and 3l refers to how many layers the jacket is made from. A 3l jacket will have an aditional layer inside to help protect the membrane from dirt, oils and sweet. If the membrane gets clogged the breathability of teh jacket can be effected as can the waterproofness. Having an adtional layer adds another layer of protection for the membrane so you may find you need to wash the jacket less often. Having an aditional layer may also make the jacket slightly harder wearing but this is not usually the main reason to use 3l.