For a long time, I have been using Amazon AWS because of Elastic IP.
Elastic IP allows me to keep an IP address even when my instance of virtual machine has stopped. When I start up the instance again, I get the same IP address.
This is useful when you have a DNS recording pointing to your virtual machine. Without the elastic IP, you have to keep updating your DNS record to reflect the different IP address you have been assigned for your instance of virtual machine.
There are other solutions such as dynamic DNS.
Here is how to do equivalent of “Elastic IP” with Windows Azure:
On Windows Azure side, there was some solution back on 3/4/2014 “Set Azure VM Static IP Address”, via PowerShell.
On 5/14/2014, Microsoft supports Reserved IP Address.
Competition is a good thing.