Private Company can get itself converted into Public Company at its own free will whenever it wants to expand & require more funds. The fundamental difference between Private and Public Company is that the Shares of public Company are freely transferable as against the shares of a private company and the investor has an easy exit option available at his discretion whenever he wants to encash his investment. Further the maximum number of members a private company can have is limited to 200 whereas there is no such limit on maximum no. of members of a public company. Which means a public company can raise capital from public through Public Issue. Hence capacity to generate funds from public at large is greater with public company. Apart from raising share capital, it will often find itself in a better position when looking at other likely sources of finance as there are more regulatory compliances to be done by public company which ultimately leads to greater transparency & public faith.
Conversely private company cannot go to public to raise capital by issuing shares as the same is prohibited under Law.