Just to expound on what Trackrat said, condenser mics are generally more sensitive than dynamics, and will tend to pick up more room noise. The plus side is that they also pick up more detail and presence in what you are trying to record. On most voices and styles of music, this is a desirable thing, but it does require a quiet room to record in. Using a highly directional mic to pick up only the source and not the noise will only work if the noise is very directional, and there are no reflective surfaces in the room. This is usually not the case, and the directional mic will only diminish the signal to noise ratio slightly. That leaves you with two options, either find a way to make the room quiet, or build an inexpensive Iso booth in the room. This can be something as simple as a PVC pipe frame and some heavy blankets, which can be put up and taken down at will.
In my opinion, any halfway serious home recordist should have a condensor mic.......at least one. These days there are some pretty good ones for very little money. Keep in mind that most condenser mics require phantom power, so you will need a preamp or mixer that supplies it.
Good luck, RD