Are there any functional differences between a (PaaS) website and a (IaaS) VM running IIS? <p>We're moving our operation to Azure soon but we'll be going for a IaaS to effectively emulate our existing physical data center setup. This is largely because our (.NET) website has not been tested using the Azure Website platform and so we can't guarentee it'll work as expected however I'm curious as to how a running a website via a Web Site service (PaaS) would be any different to running it on an IaaS style VM which runs IIS. Isn't it functionally the same? Is it really necessary to test for both PaaS and IaaS deployments?</p>