Again, there is no one right way to farm. By its very imposition on a piece of land agriculture disrupts the local ecosystem. Do organic farms use pesticides? Yes. Are organic foods healthier. No. Is organic farming better for the environment? Maybe not.
Read more about conventional farming and organic farming in this Scientific American article http://blogs.scientificamerican.com/science-sushi/2011/07/18/mythbusting-101-organic-farming-conventional-agriculture
An organic farm can use pesticides but do not do so as a matter of course where as a conventional farm has a strictly planned application schedule that adds chemicals at particular points regardless of actual need. this makes a big difference in terms of the rates at which pests become resistant to pesticides. A conventional farm uses high availability fertilizers to allow much less crop rotation which has a major negative impact on the overall health of the soil requiring continuous and increasing fertilizer additions over time. the organic farmer uses fertilizers and crop rotation to improve the long term health of the soil.
Many of these distictions do disappear when comparing large factory organic farming as they are organic largley in name only.
in terms of whether organicly produced food is healthier than conventionally produced food I don't think that we have been using the level of ag chem that we use today long enough to know the real impact. molecular analysis only tells part of the story. Certainly our population has been getting less healthy since the 'green revolution' that introduced all these ag chemicals to us. but that could also be the effect of many other things.
Bio dynamic farming absolutly has less negative impact on the environment in which it is practiced and rarely uses pesticides or fertilizers per se at all.