Anith Gopal

if every tenant is hosted in its own web application : pros : 1- separate web.config 2- separate SLA (like access channels, zones, etc…) 3- separate management for IIS (since IIS can see the wep application level) cons : 1- different socket (IP:Port) even if we have to use host headers. it is a separate socket 2- aloooooot of overhead for managing diff web apps 3- not scalable (when we reach a large number of tenants we cannot provision each one as a web app) as compared to site collections 4- share same web.config 5- some IIS features (example bit rate throttling) will only be configured per web app  

See the rest here:
SharePoint 2010 – Hosting a Tenant in a Web App vs Site Collection