The primary benefits of the public cloud are:
1. Easy scalability: One of the main benefits that comes with using public cloud services is near unlimited scalability. The resources are usually offered 'on demand' so any changes in activity level can be handled easily. This in turn brings with it cost effectiveness.
2. Cost effectiveness: Since a data center houses hundreds of customer businesses, the hardware and software works out cheaper.
3. Increased reliability: The vast network of servers and the wide bandwidths with which they are inter-linked in public cloud services offers better reliability when compared with private cloud. Even if one data center was to fail entirely, the network simply redistributes the load among the remaining centers making it highly unlikely that the public cloud would ever fail. Also, data centers put lot of resources such as power backups, and backup servers available all the time to cater to any unforeseen events.
The main advantage of private cloud over public cloud is with respect to security. Since the public cloud is available on public Internet, it is possible that hackers may attempt to break the services. A private cloud uses its own server farm, and connected to others resources using private lines, such as a leased line or a VPN.