The major problem with this restrictionist philosophical method is that you end up being a Procrustes. Focusing on one part of the data at the exclusion of other parts means that you end up with a half truth. The cost/benefit is this, the more object knowledge you have the less subject knowledge, the more analysis the less syntheses, the more quality the less quantity.
For example, you can reduce music down to its objective elements. You can say that this song has this frequency and then this one and then the next. But by doing this you kill the existential aspect of the song. The subjective element is what makes music, music.
Soren Kiekegaard talked about how the more objective a fact is the less existential personal relevance the fact has and vise versa. The fact that 2+2=4 is highly objective but it has little meaning to me on an existential level on the other extreme my eternal salvation has a lot of existential importance to me but it is unprovable. A philosopher to sacrificing the intuitive (existential data) comes at too high of a cost. A philosopher is a lover of wisdom, as such a philosopher needs not to look for a wisdom to serve him/her but a wisdom to serve. The truths found by a restrictionist philosophical method are below man and are not worthy to serve. Link