Currently moving to Amazon EC2 from another VPS provider. We have your typical web server / database server needs. Web servers in front of our database servers. Database servers are not directly accessible from the Internet.

I am wondering if there is any reason to put these servers into an AWS Virtual Private Cloud (VPC) instead of just creating the instances and using security groups to firewall them off. 

We are not doing anything fancy just a typical web app. 

Any reason to use a VPC or not using a VPC?

Thanks.