Answer:
From a relative point of view we will always perceive the duality of existence as it appears to our ego-driven natures.
From this position we are accustomed to success and failure, day and night, good and bad, advantages and disadvantages, but to the saint who is ever awake in the great cosmic dream these attributes melt into the sea of Satchidananda - Bliss Divine.
Likewise, from a transcendent viewpoint one could say there are NO disdvantages to spirituality, because it is all happening in the NOW. Now, we are born, now we live, and now we are united the veritable essence of God itself. From perfection we came. Perfection can only manifest perfection and therefore we must already be perfect...in essence. All things work exactly according to law to spiritualise mass. There is a reason for every apparent incident, whether good or bad. Even disadvantages when viewed correctly become challenges to the soul from which it might learn to manifest its divine potential.
From a relative viewpoint, which applies to most people on earth, I can think of a few 'disadvantages' to spirituality.
One is loneliness! I'm afraid this is something one has to put up with for a time. Many great sages have testified to the fact that in their search for God they have detached themselves from so-called civilization in order to experience the divine truths within. This can make one quite lonely for a time, but this is a passing phase in spiritual living. Even those who have worked hard at their spiritual practices and yet chose to remain 'in the world' there is still an element of loneliness for many reasons which you will discover.
Another is lack of popularity! Strangely enough, the greatest men and women throughout history and even in these modern times who have done a great to spiritualise the world and help others to find the light within have virtually made themselves unpopular in the world. Even those who propound a spiritual solution to world problems are regarded, by on large, strange and eccentric! The world, finds it hard to accommodate new ideas! Actually, the ideas are old but its the practice which needs fresh expression! A spiritual aspirant learns to detach from the bias of personal or public opinion, if it means doing the right thing.
Oversensitivity is yet another. The greater one develops spiritually, the greater becomes our ability to sense and feel things deeply. This is the reason behind the need to control our emotions and feelings. As we attune to higher energies both within and outside ourselves we become extremely sensitive to the vibrations of people, places and things we come into contact with. An unbalanced mentality might become unduly affected by this new found spiritual attribute which can manifest in many different ways. Whether this manifests in a positive or negative way depends on the degree of training and control one has.