Magnetic reversal or geomagnetic reversal is the process in which a planet's magnetic poles reverse their polarity. That is, the magnetic reversal on Earth will mean that our magnetic North pole will become the magnetic south pole and magnetic south pole will become the magnetic north pole. It also means that our compasses will be off by 180 degrees and will point in exactly the opposite direction (north instead of south and vice-versa).
It is a fact that magnetic reversal is a common process and has taken place several times during the history of Earth. The last known instance was about 800,000 years ago.
Before we think about the pros and cons of this process, one has to understand that the process takes a long time and the field does not change overnight. This means that living beings will have sufficient time to adapt to this change (thousands of years). Thus, any notion that magnetic reversal may be dangerous to birds (such as pigeons) who use Earth's magnetism for direction is not true. The flip will occur over several life times of such birds and they will have sufficient time to adapt. Magnetic reversal is also not estimated to affect the incoming solar activity (such as solar flares and coronal mass ejections).
Thus, there are no significant advantages and disadvantages associated with magnetic reversal.
Hope this helps.