The question of whether to use a filtered pipe or not is more complex than it appears on the surface. One general recommendation would be that if you are going to inhale (not the best idea), use a filtered pipe to reduce the amount of tars and nicotine.
Next, let’s look at the distinct types of filters. There are two main categories of filters- pass-through and pass-around. The pass-through filters are the ones most people are familiar with, like Dr. Grabow or Medico. Those filters use a paper or paper/charcoal element to remove particulate matter from the smoke. Other types of pass-through filters include charcoal or silica gel versions (usually 9mm for European pipes). They serve the same function as the paper kind but use varied materials to do the same job. Most people who don’t inhale don’t like this type of filter as it reduces the flavor of the smoke. Some people will buy this type of filtered pipe but will remove the filter. Due to the physics of air movement, this is not the best idea as a filtered pipe without a filter will tend to smoke wet.
The pass-around filters are usually made of wood (balsa or maple), and their whole purpose is to remove excess moisture from the smoke. Savinelli pipes use either a triangular 6 mm filter (U.S. market) or a rounded 9 mm filter (Europe and elsewhere) made of balsa to do the job. Brigham pipes use a maple filter to serve the same function. These filters are unobtrusive, and most people find that they don’t affect the flavor of the smoke. Savinelli, in most models, gives you an option, however. They include a 6 mm rod of material with a smaller hole down the center. This is inserted in the place of the filter and basically, turns it into a non-filtered pipe.