Each Cloud Server comes with the simplicity of a dedicated and persistent public IP address (no NAT) with a second, private IP address for free. There is also low latency bandwidth between your Cloud Servers. Additional public IPs are available upon request and shared IPs can be provided for high availability.
With EC2, the IP configuration is more complex. Each instance gets a non-persistent private IP address NATed to a public IP address. When instances terminate and new ones are launched, a new private IP address is assigned which means you need to plan for changing private IPs (although Elastic IPs can be remapped). In addition, only one NATed IP address is available which, for example, does not lend itself to hosting multiple sites via SSL.