From what I believe either way is fine... plants are not affected by the amonia (or that is what I was told) and they can actually help the cycling process speed up because they carry beneficial bacteria from the store to your tank! Hope that helped!
You should never fishless cycle a tank with plants. If you wish to fishless cycle then do it before you add any plants and in the dark. Adding ammonia to a tank with lots of light is asking for algae trouble.
If you mean cycling your tank using fish then the addition of lots of plants it a good thing as the plants will use up the ammonia. This method is best done by adding the fish slowly and feeding sparingly.
Before !!! Besides the points mentioned by nukeonekitty, this gives the opportunity for the plants to get established so when you add the fish they will not be uprooting them easily.