We did not try any other solutions beside Illumio. There are two main difference between the products:

1. With Illumio, you have to install an agent on every server, and you don't have to do that with ShieldX, because it is agentless. 
2. The ShieldX GUI that you log into is much easier to move around in than the Illumio user interface.

Both products are pretty low in cost. However, ShieldX gave us a better deal over three years, which played a role in our choice.

We evaluated vArmour and Illumio. They didn't meet our requirements. ShieldX is a superior solution and I can give you the quick differences: Illumio is really an orchestrator so it's not providing security controls. It is managing the security controls provided by the operating system. It manages Windows Firewall, for example. vArmour, which is a closer comparison to ShieldX because it does provide security controls inside of the virtual environment, is one of those monolithic firewalls, so it does not scale as well.

We looked at other vendors. We look at our existing vendors, how they are shaping up in the cloud, and the advances they have made. 

We looked at ShieldX and another competitor. It's typically going to be the incumbent plus one or two new challengers.