Unfortunately a direct answer to your question is not available. Both organic and inorganic fertilizers have advantages and disadvantages and I would say that the type of plant, geographic location, and personal preference add to which fertilizer a person may choose to use. The job of a fertilizer is to readily supply nutrients to the soil that will aid in plant growth, these elements often include nitrogen, phosphorous, and potassium. Organic fertilizers are often made of natural ingredients (manure) but can also be synthesized chemically using derivatives from living things. Inorganic fertilizers are all produced chemically - but most are derived from minerals. The inorganic fertilizers are good at providing the right amount of nitrogen to the soil and do so pretty quickly. They are usually cheaper to buy and it is argued that the might be more efficient in aiding plant growth. However, the downsides include acid formation, leaching (so leaving the soil and contaminating water through rain/flooding), and they must be applied pretty frequently. Organic fertilizers generally do not produce nitrogen quickly, and they can be applied infrequently, as well as they are less likely to be leached from the soil by rain. The downside to the organic fertilizers is that they do not do so well in cold weather, some contain the seeds of weeds, and their is a slow response to fertilizer application and plant growth. If you are interested in more about fertilizers here are two websites that give a lot of unbiased information.
Fertilizers
fertilizers

The limiting nutrients in soils tend to be nitrogen and phosphorous, rarely sulfur. Everything else the plant can get from the air. All living things contain all three of these elements (this is why they are necessary), so dead material from formerly living things will have everything the plant needs. It's possible to have more of these things than is typical for living things, however, and different living things have more of them than others. Animals, for example, have more protein, hence more nitrogen and more sulfur, per unit mass than plants do, which are mostly carbon, hydrogen, and oxygen. As a result,composted animal material will make stronger fertilizer than composted plant material if the limiting nutrient in the soil is sulfur or nitrogen.Any natural fertilizer will thus have everything the plant needs, but some artificial fertilizers might have more of particularly needed nutrients than others

This depends on what you mean by effective. Measured by weight, most organic (made only from natural sources) fertilizers help plants grow pretty much the same as they would using normal fertilizer. The main differences are that organic fertilizers usually have fewer contaminants from pesticides or heavy metals, but they also cost more, and they are harder to make.