The drawback is the tendency to get involved in Breslov which is filled with insane people.
For me personally I was not lacking anything as a straight Litvak. Torah and marriage, Israel, devekut,... Getting involved in Breslov changed all that. It is like a door is opened to all kinds of other cults and bad stuff.
The other thing is there is even in the thought of Reb Nachman itself a tendency is to reject the balanced approach of the Rishonim (Rambam, Obligations of the Heart, Musar) of synthesis between Reason and Revelation. This is possible to find find in the words of Reb Nachman himself through quilt quotations.
This is not to minimize the importance of Reb Nachman's thought, but it does mean that it is highly advisable to avoid Breslov and all the cults that were put into excommunication by the Gra. Reb Nachman himself was not included in the excommunication, but getting involved with his books tends to open the door to lots of other pretty bad stuff.
Reb Nachman's system is is a synthesis of straight Litvak Torah, Gemara Rashi Tosphot, with the Ari.
The Rambam's is a synthesis of Torah with Aristotle. The differences are significant and that leaves me wondering .