SharePoint 2010 - Hosting a Tenant in a Web App vs Site Collection

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